I met someone from South Africa back in 1981 when aparthied was still going strong. She told me that black people she'd seen acted like bullies, and were rude, loudmouthed and coarse. She asked me if they acted that way in the US. I told her some did, most didn't, but if I were made to feel like mainstream society would be happier if I'd just disappear, I'd probably act that way too. I think there was and is a lot more going on than that, but I think it's true that if a society forces a group to remain apart, it's bound to turn into an "us vs. them" situation.