I don't know about common, considering where I live. I've see every shade of ethnic color from the rainbow, and I'm even pretty sure out of all the people I know, and of all the friends I've made (or even, ever made) I've met practically every ethnicity you can think of. Maybe not every combination, but indeed A LOT of ethnically different people of all kinds, and I've never met such a racist person, especially a black one, in person. I have met racist people, but not as racist as this guy. Maybe it just depends on where you live, but I have to purposely go to the right city LOOKING for trouble, to experience racism or discrimination, and this is of course assuming pretty much that I know exactly who's door to knock on.
Of course, that isn't to say that I haven't met a teacher or two within public school without the back bone to say anything to the group of noisy black female students, but I guess it would have looked bad if a white teacher told of a group of black student right?
It doesn't piss me off, I was just very surprised. It was like that moment in a video game, when you finally figure out how to make a puzzle you're stuck on work and you say to yourself "*gasp* Ohhh, now I get it."