This is the result of many little things.

When I have argued about them in the long ago, many of the response at the end would be, "lets not make a mountain out of a mole hill".

First, we got rid of ethics. Remove church from schools, but they didn't replace what they removed. They just left everyone to figure it out on their own.

So, along comes solipsism and moral-relativism. And people didn't have any ethical training to understand why this could be a bad thing.

Then you get to the end (skipping a few steps) where people hate other people for what they feel is oppression. Whites are bad because long ago, whites had black slaves. (forgetting all the rest of slave history) So now, they are the bad guy. They have to either change their ways or die. And they will never change their ways, so they should die.

It is the inevitability of dehumanizing the opposition with no morals or ethics to maintain ones balance.