Belz...
Fiend God
I think it's just the innate defensive response when people feel that their group is threatened by another group. But that doesn't mean that we as a society can't learn the difference between rational responses to real threats and chauvinistic xenophobia.
Of course, but that doesn't change the innate nature of this sort of behaviour.
I mean, the need for reproduction is probably the most innate thing we have and yet we don't typically seek to hump one another nonstop.