I have noticed this for years. I say people are not racist, homophobic, etc... People just want to gang up together and the existence of a group reaches the height of its meaning (to its members) when they can say "This is us. That is them. Clearly we are different (superior). Don't mix us." Same is true when you have 10 Harvard grads with 5 "insert_your_state_university" grads in the same room.

The ultimate test: Take a hispanic who hates blacks. Add a black who hates whites. Add a white who hates hispanics. Leave them stranded in the desert and they must rely on one another to survive. They will be friends in no time. When they get back to town it will be "This is us, the survivors. That is them, those who never had such an experience. Don't mix us."