While I don't agree with racism, there's some discrimination that I agree with. For example, the people that argue that you should never discriminate against someone - what about in extreme cases? Lets say there's a murderer who kills my family. Should I not discriminate against him because he killed my family? lol.

The same goes for how stereotypes form, and how racism occurs. Something bad happens because of a few people, so now you hold a personal discrimination against that entire group. It's a bad thing, but it happens - I personally don't agree with it, like the idiots who call all Muslims terrorists and all of that stuff.