Soundwave on 12 August 2013
Unfortunately I think it's a dark part of human nature/evolution.
We're a tribal species by nature, you put a human in the wild and physically we're rather mediocre and would get eaten alive by many predators in the wild, so the successful humans were likely those who roamed in packs (tribes) and were loyal to the tribe.
But that create tribalism, and humans tend to feel threatened by other tribes, I think that evolutionary hardwiring still exists.
Granted we've made tremendous progress and our brains have evolved tremendously too, but it's very easy to fall into the traps of xenophobia, racism, "us versus them" type thinking.
