Can't say it's happened to me IRL, but I live in Montana (which is moderate/conservative heaven on earth). As far as online goes, I've seen people apologize for being white, people tell people they should feel bad they're white, and so on and so forth (in comments and video clips).
I agree it's mostly the fringe who spouts this craziness, as with most things in politics, but when you see it and then see that my town of Helena, which is probably 95% white/hispanic, has a black mayor (cool dude, BTW) those generalizations really irk you.