Food for thought:
Tribalism is the default state of humanity. Every other form of extremist behavior is a realization of that: Racism, Homophobia, Islamophobia, antisemitism, bullying, (fill in the blank)-ophbia, heck even the all or nothing in the political divide .. all the same thing. We are programed to find out what's different.
We seek out what's different from us and attempt to remove it not out of hate but an unconscious survival instinct. We are ensuring our tribe receives the resources it needs (the bottom tiers of Maslow's Hierarchy of Needs). This instinct dates back to the days where we lived in the jungles and we competed for food, shelter, mates, etc. The world may have changed but the genes that made it a survival instinct for thousands of years are still there and we all act on them, consciously or unconsciously.
I am not condoning the behavior. I am not excusing the behavior. I am trying to understand the behavior.