I think it's mostly atheists filled with hate.
Agnostics are mostly indifferent.

Personally. I grew up in very rural AZ -- Mormon country. The LDS church colored every aspect of life in our society.
For example, the local school teachers would talk about the 'Mormon Mafia' . They all knew that you never punished a Mormon child unless you wanted 10 phone calls the next day and weeks of career level trouble yourself.

For a group founded by a convicted fraud artist (Joseph Smith) and full of laughably false promises and claims, they are very detail oriented in their desire to rule and end the world.

Personally again. I try to avoid the word 'hate'. But I'll admit that I don't have anything positive to say about them. Ample experience has left me with nothing but ill will.

It would take to long go through everything but here are a few simple google topics to give you an idea

1. The Magdalene laundries
2. Ecumenical Child abuse in religious institutions
3. The LDS evergreen international experiments in gay conversion therapy
4. Deaths of Children and infants caused by Witch exorcisms in 20th century western churches including the UK and USA
5. Religious Honour killings.

I do not hate what isn't there. I personally am a vocal Atheist, but was brought up within the Catholic fold for my formative years. It was through critical thinking that I started to see plot holes in religious dogma. I was actually told by a catechism teacher that "I thought too much," and it was definitely not meant as a compliment. The thought of just "shut up and take it" made me even MORE inquisitive and prone to critically think about what I was being taught. As a rebellious teen and through a good portion of my adulthood I was a Buddhist, (after much research, understanding of Buddhism) and I thought I finally had found my niche, and for a while, I did. But those hard questions still kept not being answered. It was never enough or a satisfactory answer. Not until I picked up Cosmos by Carl Sagan and I read it that's when it hit me. From that point on I had to do a small jump, and be fully honest with myself and realize that there was never going to be a satisfactory answer to made up things. After that, I've been vocal about my Atheism and I have never looked back. It's been such a life changing experience, in the most positive way.

A lot of atheists are not big fans of religion and with good reasons. Religious people themselves are good people. I have no problem with most individuals, but the beliefs themselves are all based around feelings and not facts. Beliefs that want us to stay in the dark ages and not move humanity forward under the circumstances that we know to be true about society and about the natural world.

Do you hate cancer, but not hate cancer victims? There you go. Believers think it is an attack on them, and sometimes it is, but often it is an attack only on religion itself - and those who take it personally are letting their own ego's do that to them. I can read history, and know what religion does to us - and hate it, but there are many believers who I care for.

Most of the people I met in my catholic days were sweet people, gentle souls who would give you the shirt off of their backs if you needed it. They were also, however, judgmental and quick to criticize and ridicule. It was the Jesuits when I went to college who gave me the mental and philosophical basis to reject religion outright, and catholicism in particular, so to that extent I sort of owe them - I might still be on the circular path (I might not, too). Where religious people run afoul of me is when they try to force their beliefs on others, or hypocritically do privately what they condemn publicly. And mega church pastors or rabidly anti-LGBTQ zealots, ok, I hate those assholes. But normal religious people, I don't hate. However when I discover a reliance on magical thinking rather than logic and knowledge, I hold those guys in very low esteem.

Faith is the enemy of reason. I don't hate religion... I do think it makes people stupid

Way too many leftees conflate HATE with TRUTH. No wonder we are in such deep shit.

Why should we not despise that which has sought for centuries to suppress, repress and even eradicate us from the face of this planet?
No-one truly knows for certain how many Atheists, etc, perished in centuries past due to the Genocidal Zealotry of Religions.
Even to this day we are still somewhat persecuted and subjected to endless and monotonous preachings, etc, via EVERY media available and by door-knocking, God-botherers trying to convert us and bring us into, what I view, as their Totalitarian realm, aka, religion.

Human beings need reasons to fight

Your post puzzles me. You ask "Why all the hate?" but then follow it with "Im(sic) not saying it isnt(sic) justified"

If it is justified, then why the question?

It is justified. And as someone else reminded us, the religious folk used to burn people at the stake (and many still would, given the chance and today's Trump-inspired hate-filled climate). Religion needs to be seen for what it is - a mental illness, propagated by our parents and those who profit from it. Religion needs to be outlawed, and removed from society.

What your witnessing has only happened over the last three or four months. Many of the erudite people don’t seem to post much these days and there is a plethora of what you describe.

Good luck with your stay and there are a few nuggets within the mire. The music groups are particularly good.

I also hate people who light other people on fire. I always have.

I would guess because religion was or continues to be used as a weapon or abuse tactic against people and made peoples' lives more difficult than they needed to be. I cannot stand self-righteous, willfully ignorant christians because they remind me too much of "family". And the actions of the careless religious during covid 19 is making me lean more and more towards anti-theism.

Nope, don't hate, just angry at them.

Ok, lets talk about the "resentment" toward flying clowns. I hate the people who try to pass the laws to make us respect the flying clowns. I don't hate flying clowns. They don't exist and any logical adult knows that.

Since age 13, I have been an atheist. I realized the Bible is just a book of stories or fables like Grimm's Fairy Tales.

Beginning at age five when I had to go to Sunday school, I scoffed at ridiculous Bible stories: Jesus rose from the dead, a woman turned into stone, parting of the Red Sea, Noah's Ark, etc. Inwardly rolled my eyes.

Michigan had a hard winter when I was 13. Bored and restless, my brother Lee, 10, and I read the World Book Encyclopedias together.

I was inspired by rational philosophers Spinoza and Descartes. They were bravely anti-theist (anti-gods), anti-church and anti-clergy in the 1600s when heretics were burned at the stake. They had to go into hiding.

The writings of rational philosophers Spinoza and Descartes inspired the European Enlightenment. The Enlightenment Period of the 17th and 18th centuries emphasized science and reason over faith and superstition.

Photo: Age 13 with my sister Beth, 7. Echo Lake, Michigan

You can't hate what doesn't exist... I do however despise the followers of religion who are destroying this country... Mostly what you see id people of like minds joking about the nonsense religious nuts believe and are afraid to question... Better you stop looking in the mirror and realize the hate is from theists towards us... Because "hate is always fear in drag..." Spider Robinson

In my life I have met many religious people of many faiths who hate & distrust anything not of their faith and they distance themselves. I have also met many who embrace differences (fairly rare breed). Hate & distrust is met with hate & distrust, not love nor indifference. The only thing to do is to have patience. If they can overcome their prejudices, good; if not, then let them go.

"Fear is the path to the dark side. Fear leads to anger. Anger leads to hate. Hate leads to suffering." -Yoda

ah. Anger is a phase you go through. And this is a safe place to vent. People need a place to express themselves after so many years of deceit.
There is no polite way of dealing with anger. its personal. I'm mostly past it. But it takes time. years sometimes.
And we here welcome the rage and vase throwing. We can relate. Go for it.

What Paul4747 said. My exact same thoughts.

Raised by atheists & used to shocking people, I don't have animosity towards them unless evangelism begins. A reasonable discussion without shunning might be in order.

I do spend a lot of time on here but don't think that much about religion otherwise. I can hardly take offense at people being angry at religion since their anger is justified. Religion is really that bad. I do take offense at the few islamaphobes who make it the sole object of their hatred. Islam is just a bit more primitive, it will evolve and there will still be islamists who are just like christian evangelicals. No religion is to blame more than any other, they're all horrendous.