Christians were not the first to think and advocate along these lines, nor does the subsequent behavior of thoroughly and explicitly Christian kingdoms evoke these ideas.

I’m not sure whether the OP is an instance of the now-familiar and tiresome Christian claim that ‘You atheists secretly believe in God even if you deny it….’ or a criticism of social justice because it is allegedly connected to Christianity, along the lines of ‘master morality versus slave morality’ critique.

In nature, Inter-species altruism certainly occurs, and critters know nothing of any god or religion. Humans exhibit it more because of our intellect and culture, but the behavior seems to be independent of any particular religion and those without religion tend to be more broadly compassionate than those who are religious.

I will always believe that a mature mind, open to considering many factors of any situation, can not only determine what is right and wrong, but can also understand that an act in one scenario can be wrong while right in another scenario. Murder versus self defense. Religion is completely unnecessary in a human using their intellect. Religion will always be only an interference to the functioning of a mind that has allowed itself to get too close.

Why do people take it for granted that one has to be Christian to be a decent human who cares about others?

This seems to me to be crediting religion, and in particular, christianity, with influenceing social interaction in a good way....toward bettering human nature....if I right.....how fucked up is that????

This makes no sense to me. Christians, at least many of the ones in the U.S., make excuses and attempt to justify slavery, have had a history of discrimination against blacks, gays, women, and minorities, have a history of being against equality for blacks, gays, women, and minorities, have a history of being pro-gun and helping create a culture of almost daily mass shootings in the U.S., and a history of censorship and banning of media.

Christians are altruistic and in favor of justice but ONLY their very narrow view of justice and only toward those they deem are deserving. They oppress the weak. They didn't rally support for refugees coming into this country. They supported locking them in cages like animals. Christians care only about their own selfish interests and not the greater good.

Your example of slavery is not a particularly good one as it is only recently that Christians have been anti slavery.
You may have parasite in your brain but I definitely do not. I was never indoctrinated .

Granted, there was from the beginning a strong altruistic theme in Christianity, and that that helped to influence, and inspire, the western cultures which followed it, to begin developing ideas like social justice, socialism and the idea of a larger "we". But Christianity was not alone in that, you can find the same philosophy in many systems including Buddhism and Stoic philosophy, and those ideals were only realized to any degree in the west, quite recently, following the industrial revolution, which created for a while spare wealth and education, beyond what the ruling classes could use for self indulgence. Who knows if those other cultures, would not have done the same, given the same economic opportunities at the same stage of cultural development.

But more than that, a thought system's flagship idea alone is never all there is to it, and even the best intentions can lead to terrible unforeseen consequences, look at Marxism which was intended, as perhaps, an even more altruistic ideal than Christianity, but which as we all know, often had truly horrible consequences. And the peculiar weakness and corruptibility of Christianity was also built into its basic ideals from the beginning too. As you ask. "why should someone from the ranks of those in power buy into it and mentally identify with the weak and the oppressed?" And the answer is, because they saw from the very beginning, Christianities in built proneness to favour and foster corruption.

The reason being, that the ideals of altruism claimed to be at the heart of Christianity, are, as everyone instinctively knows, impossible in practice to realize. Which means that everyone is bound to fail, even the saints probably failed in reality, in living to that level of perfection, whatever apocryphal myths about them may say. Which means that the other great theme of Christianity, that of total and cheap forgiveness was a very inherent part of the system from the beginning. It had to be, because without it nobody would have adopted it.

Which had two effects. First it excused the rich and powerful anything they may do, however corrupt and harmful. The only real crime, being an unwillingness to pay the price of forgiveness, whether in cash or penance. Creating thereby a culture which held no one responsible for anything, and which honoured corruption, especially among the rich and powerful, who could more easily buy forgiveness, not simply with cash, but also with time, commitment and display, all of which are much more readily available to the rich and powerful than to the poor. Thus the twin crimes against the poor and weak, the catholic oppression of those unable to easily buy forgiveness by those controlling the market in it, and the Calvinist view that weakness and poverty were the result and proof sin, were there from the start, as well as the failed attempt at altruism.

And no doubt that, willing acceptance of corruption and dishonesty often helped the Christian west to overcome other societies where they were not understood, many of the cultures easily overcome by the west were politically naive, while it tended to be the older, also corrupt, cultures, such as those of the far and middle east, who largely but not entirely survived unscathed, the eras of western expansion.

Which is why in the modern world, the idea of social justice, which today has far better ideals and far better understandings of human nature, economics and psychology to support it. Does not any longer gain anything from the Christian prop, and would be much better served, supported by those modern thought systems alone.

Well if you want to give Christianity credit, give it to the only place it is due:
For taking everything that came before it in human history and taking credit for it.
(And also claiming that there is only one god and worship on sunday....But I assume those are out of context here))

Now of course, I have just "railed" against it

Christianity has justified many of its atrocities with lies, and you are trying to justify Christianity. Here is one example:

The Myths of the Thanksgiving Story and the Lasting Damage They Imbue

What is the Thanksgiving myth?

The myth is that friendly Indians, unidentified by tribe, welcome the Pilgrims to America, teach them how to live in this new place, sit down to dinner with them and then disappear. They hand off America to white people so they can create a great nation dedicated to liberty, opportunity and Christianity for the rest of the world to profit. That’s the story—it’s about Native people conceding to colonialism. It’s bloodless and in many ways an extension of the ideology of Manifest Destiny.

What are the most poignant inaccuracies in this story?

One is that history doesn’t begin for Native people until Europeans arrive. People had been in the Americas for least 12,000 years and according to some Native traditions, since the beginning of time. And having history start with the English is a way of dismissing all that. The second is that the arrival of the Mayflower is some kind of first-contact episode. It’s not. Wampanoags had a century of contact with Europeans–it was bloody and it involved slave raiding by Europeans. At least two and maybe more Wampanoags, when the Pilgrims arrived, spoke English, had already been to Europe and back and knew the very organizers of the Pilgrims’ venture.

Most poignantly, using a shared dinner as a symbol for colonialism really has it backward. No question about it, Wampanoag leader Ousamequin reached out to the English at Plymouth and wanted an alliance with them. But it’s not because he was innately friendly. It’s because his people have been decimated by an epidemic disease, and Ousamequin sees the English as an opportunity to fend off his tribal rebels. That’s not the stuff of Thanksgiving pageants. The Thanksgiving myth doesn’t address the deterioration of this relationship culminating in one of the most horrific colonial Indian wars on record, King Philip’s War, and also doesn’t address Wampanoag survival and adaptation over the centuries, which is why they’re still here, despite the odds.

There's this tendency to see the English as the devils in all of this. I don't think there's any question they’re in the wrong, but it doesn't let them off the hook to say that native people wouldn't take it anymore. And regardless of that, I think the evidence shows that native people had reached their limit and recognize that if they didn't rise up immediately, they were going to become landless subordinates to English authority.

This is about as contrary to the Thanksgiving myth that one can get. That's the story we should be teaching our kids. They should be learning about why native people reached that point, rather than this nonsense that native people willingly handed off their country to the invaders. It does damage to how our native countrymen and women feel as part of this country, it makes white Americans a lot less reflective about where their privilege comes from, and it makes us a lot less critical as a country when it comes to interrogating the rationales that leaders will marshal to act aggressively against foreign others. If we're taught to cut through colonial rhetoric we'll be better positioned to cut through modern colonial and imperial rhetoric.

Full Article: [smithsonianmag.com]

Another reason why Republicans do not want history taught.

Ridiculous.
Christianity has been the driving force behind social injustice far more than any thing resembling rational thought.
Burning witches was social justice?
Justifying slavery was social justice?
Claiming that the North American continent was intended for white men all along, so genocide of millions of people to "cleanse the earth", was blessed by manifest destiny was social justice?
Laws against integration and miscegenation were all based in white christian bias and racism. Social justice?

Horsefeathers! Could you base your Extremely Dubious conclusions on any More false assumptions? Doubt it!

Another load of crap. First you define "natural" and "unnatural" in what appears to be your personal opinion instead of any real justifications. Then you go off making ridiculous assumptions based on your personal opinion. A white person in London should care about the abolition of slavery in 1830 for the same reason a white person in London today might want to fight against Russia invading the Ukraine, the ability to empathize with the suffering of other human beings. It has nothing to do with "justice", it has to do with the simple ability to not be a narcissistic asshole.

The reason is quite simple: what we call 'social justice' is a specific Christian idea, maybe even the most powerful idea of this religion.

The ability to empathize is not Christian, it's human.

In one sentence: Social Justice Humanism is the continuation of Christianity by other means.

And one day you might be able to make a cogent argument for that, but you sure haven't done so yet.

Jane Goodall in an interview was talking about interactions within a group. I can not remember the specifics but in it she talked about a find of a leg bone that excited her and showed that the members of the group had a social structure and cared about each other. The bone showed a fracture that had healed. This meant that the rest of the group cared for and helped this individual get better. I am pretty sure the group she was talking about did not show any evidence of christianity. Yes I know this is the larger "we"

In many christian societies this did not happen in fact those within the society who were different were ignored or treated badly.

I think it is important to remember that the ones fighting for slavery were also happily going to church on a Sunday and calling themselves good god fearing christians.

Young children well before being indoctrinated by any religion will show compassion and help others regardless of which group they belong to.

From memory the bible contains more phrases about not liking those that are different than telling everyone to like and support everyone.

Back in college I studied psychology I never remember the names of the theorists but some of their words stick and one that stuck talked about a state of mind where the person acts out of what is right and what is best for everyone rather than just a self or my little group. This had a fairly profound effect on 17year old me. I started thinking along the lines of I don't matter but what I do matters. (please note I had always been a bit of a social justice warrior) I had very little indoctrination in chrisitanity and gave up on it quite early. I have broken up fights between a person much stronger and larger than me and a smaller weaker person I have stood up for someone I hated because that person was being accused of something they did not do.

I think it is an interesting issue to look at but far from conclusive.

Yep. Scapegoating is a common theme in many mythologies, but Christianity was the first, last, and only mythology in which the scapegoat (Christ) was considered innocent. Like it or not, Christianity remains the most highly evolved moral system produced by humans, whether we acknowledge it or not. It is the source of many of the unconscious assumptions that hold modern secular societies together. Scandinavian countries have a deep Lutheran foundation.

Humans are innately social. I believe there are genetic foundations for a variety of (sometimes conflicting) social impulses, including altruism and cooperation, tribalism and xenophobia. Organized altruism - social justice - can have less than selfless results such as expanding influence by forming alliances, absorbing populations, or undermining competing power structures.