There are two kinds of racism: The kind I understand and the kind I don't. :)
1) The kind I understand. Suppose John grew up in Saskatchewan in a small town near 3 reserves. On each of those reserves, there was a problem with violence, alcoholism, unemployment and poverty. As a result, most of the people from those reserves who John ran into had a lot of problems. Furthermore, John ran a small business and gave a lot of credit to both the bands and the people. Though not everyone ripped him off, it happened a lot. John decided that he shouldn't trust the Indians any more. It's racism, but it's racism I can understand. I don't like it, but I understand it.
ETA: DrDawg (whose blog you should totally read!) posted about the death of a notorious racist. I think this is a subset of the above kind of racism. It's sorta understandable in that he lived around a lot of them and drew the wrong conclusion, but instead of a distrust, it developed into an all consuming hatred. And I truly don't grok that.
2) The kind I don't understand. John decides that Chinese people are greedy fuckers, out to take over the world. He decides they're all cold-hearted bastards bent on world domination. John has only ever known two Chinese people. They were a nice couple who owned the restaurant in the town near him.
(2) is the kind that baffles me so much. Where do these ideas come from? I feel the same about anti-semitism. I understand it if you're a Palestinian, and are dealing with violence on a daily basis. But if you're hearing about it second-hand, from a biased media, where in hell do you get off being an anti-semite?
Now, that being said, I am completely okay with criticising Israel for their actions. That DOES NOT equate to anti-semitism any more than my hating Stephen Harper and his cronies and the decisions they're making on our behalf make me anti-Canadian. My special hate-on for George Bush doesn't mean I hate Americans. It means I hate the government they elected, and that I'm angry with the morons and dupes who voted for him. At the same time, I'm furious with Israel for their actions (and with Hamas, for that matter), and I'm angry with the people who support them, but I do not hate them for, as Jon Stewart would say, their Jewiness. That they're Jews or Muslims or Americans or Canadians or whatever doesn't matter a shit to me. What matters is that they're behaving like assholes, shitting on everyone around them. And *that* is why I'm mad. And no, I don't for a second believe that it's because they're Jews or because they're Muslims that they're acting like assholes. They're acting like assholes because they're human, and humans regularly act like assholes. (See: History)
Just a little aside: I grew up in Saskatchewan. I was 18 before I met a Jewish person. I was in university before I heard the word kike, and it was in a poem I was learning in English class. I had to ask what it meant. I had heard the stereotype about Jews being cheap, and asked Dad about it (I was about 10 at the time). Dad, who could be a bit of a racist, albeit a fairly harmless one, said, "Jews are cheap because they got screwed over so many times in so many ways that they're very careful to keep a lot of money around. In case it happens again. Same was as people who lived through the depression tend to hoard food." LOL. It's funny now. The concept of anti-semitism astounded me when I first really ran into it. When we learned about the Holocaust in school, I could not wrap my mind around that hatred. I still can't. I simply cannot fathom hating a group of people just because of their race or religion or colour or gender or gender-preference, etc. Now ask me to hate them for killing or torturing people, and I'm all over it. And then, it's only the actual perpetrators and their supporters. I can't make the leap from X killed Y to all Xs are murderers.
I hope I'm explaining myself clearly. It's a hard topic to get from ideas into words.