Sometimes it's religion, sometimes it's "race", sometimes it's both, sometimes it's something else entirely. It can be football allegiances for God's sake.

The point is to find a distinction between people you can work on and turn into a division, and use it to gain some kind of power, or often enough some kind of illusion of power to make up for the lack of real power.

Any time we find history and historical injustices being used as a kind of rallying point to revive anger at some other group of people we should be very cautious.