it doesn't actually feel that way to me, although i see those around me thinking in those terms. i try to combat it, gently, when i can.

g

As integrative, 'social' creatures, we can't help our instinctual drives to belong. In what ways we associate with others and the commonalities we choose to share in defining ourselves as members is what I view as the source of our flaws.

Belonging itself is considered to be something akin to proprietorship by those setting criteria for it. We really can associate with one another and bond to one another without proprietorship being part of the picture. It is a source of so many, as you point out, flaws that can be destructive; at the root of emotions like jealousy, greed, lust, pride.

Anyone pondering just where notions like colonization or slavery, or for that matter marriage, come from can find them sourced in possession and proprietorship; a making of each other into property. Objectification in this way of thinking is inevitable and the opposite of respect for others' integrity, internal affairs and fundamental rights. Nature would, in my view, have it different. Even Nature has been subdued, dubiously re-defined and colonized.

Why are we so sick? Our associations are organized and imposed from the outside artificially, in conflict with our better, natural instincts. Ever wonder how it is that animals are so loved and appreciated for their internal morality; for attributes like openness with affection, love, loyalty, protection and sacrifice? They aren't out of touch with their natures. Even if they 'set foot' in a church, mosque or synagogue, they are immune to corrupting influences that place humans at odds with their natures.

To divide and conquer. To gain control, power, and wealth, groups are divided by color, culture, religion, economics, and ethnic origin then they are assigned a value. All of this is in the service of greed. Greed is humanities greatest flaw.

Why does who "always" feel we must be black and white?

I certainly don't.

I recognize that there's no such thing as 100% objective truth.

I also recognize that doesn't make blue the same color as red, alive the same as dead, or cruel the same as kind. So I reject the crazy-making notion of a post-truth world, too.

I think some distinctions are useful while others are only divisive. Putting people into categories simplifies the world for us, which makes it easier to comprehend but less precise. It creates in-groups and out-groups, which makes groups get together but also exclude others from those groups. So it is a double edged sword.
On the other hand when we want to talk clearly about the world we need as precise definitions as possible and vagueness of terms can lead to confusion and makes one easily manipulated.