Shouldn't discussions about racism go in humanities? This is the suggestions forum... but whatever, its arnox's forum.
It is natural for groups of humans to hate those not in their groups. It happens in the wild, too, with animals and plants. With people, yes there was such a thing as different 'groups' of people fighting and hating each other, and avoiding each other, but in the majority of cases (just like today) the rival groups looked pretty much identical to each other, physically.
Too bad that all humans are part of one big group - humanity. And I would hardly say that animals HATE one another.
Furthermore it's pretty silly to say there's no such thing as racism. For thousands of years different ethnic groups have fought each other, each thinking the other to be a barbaric race of heathens. Upper and lower egypt, rome vs the goths, gauls, carthage, and well anyone that wasn't roman, the japanese vs the chinese, etc etc...
you might as well argue there's no such thing as religious extremism, just people with different views that sometimes may or may not be violent. you're not doing anything to clarify the issues, only obscure them by arguing over semantics.