EDIT: And as hedwards reminds me, I prefer the term bigoted anyway, it covers racism and the same intolerance when it doesn't apply to race (such as intolerance for homosexuals or folks of a different religion). It also exposes the silly argument that an oppressed "race" cannot be "racist" when you replace the latter term with bigoted.
The main reason I prefer that term in most cases is that homophobia, antisemitism, misogyny and other such things tend to travel together.
The other issue is that people confuse the fact that it's generally less harmful for a black person in America to be racist against a white than the reverse with the idea that somebody that's being oppressed can't be racist. Which is just plain silly. And it really does water down the intent. As well as give cover to the more hardcore out there like the neo-Nazis and other supremacist groups.
Personally, I dislike the system because somehow I should be nice to black people even if they're bashing on me for not being straight, at which point these sorts of power comparisons start to look very silly and bizarre indeed.
It always makes me laugh and cry when people say or seem to think that whites can be racists but minorities can't be racist towards whites...and when they are, it's okay because they're just getting their revenge/day in the sun/etc.
Usually what's going on there is that it's a power grab. Or an effort to rationalize the bias. There have been definite racist and general bigots out there of all races, saying otherwise makes it a lot harder to have an honest discussion and actually make any sort of meaningful progress.
Anybody that doesn't believe that a black person can be racist should seriously look up the history of the Nation of Islam. It was for a long time a pretty nasty organization led by a real nasty fellow, I'm not sure what's happened with them more recently though.