Damn, I had literally the same happen with a kid I grew up with. We were like brothers our whole lives, and then as we got older we started getting into fiercer fights and arguments.

For the last few years I knew he was becoming more radically libertarian/right wing, but I was doing the same thing in a leftward direction, so I was like, how can I judge him? But as time went on I realized how insidious and openly sociopathic his worldview had become, and that I was no longer in a position to change that in him. The last straw for me was this summer when he used slurs to refer to the protests where I was getting shot at. I haven't spoken to him since and I don't intend to, nor expect to hear from him.

But even then, say hypothetically he was at one of those protests and we socked each other in the face, how is that different from the fights we'd had our whole lives?

I dunno. Doesn't make me question my principles but certainly fucks with my emotions. Chud family is weird, man.