More generally, it's in-group vs out-group. For many people, the in-group is "white men" and the out-group is "everyone else". But this behavior is pretty baked into humans. We'll form stupid groups over anything. I was reading a book about how people change their minds, and it talked about some experiments they did. Like, they gave kids at a summer camp different colored shirts, and sure enough they formed separate groups. They had to stop the experiment when one group tried to burn down the cabin of the other group.

I don't know how to fix this.