Dude, I'm 'whitey' here too, I couldn't care less either (well, it's obvious since I live in South America!!). It's different when it comes to blacks because of the (recent) history and the general sensitivity especially in ths US.
The "50 years ago we'd have a fork up your ass" is REALLY uncalled for and CANNOT be justified....It's the same as with jews. Remember when slay showed a scene from south park and people were (generally speaking) offended as well. South Park makes fun of everything (which is why I love them so much), but 'Kramer' chose to hit specifically on blacks in that scene. in a way to OFFEND them. The 'jew gold' thing was something which comes from one part of thousands and thousands of other jokes about skin colors, backgrounds, etc, but people didn't get that because they ONLY SAW THE JEW PART, not taking into context the tons of other references south park makes (even in that one episode).
If a guy calls you whitey, honkey, snow, or as Borat put it "Vanilla face", it's not to OFFEND you. This 'kramer' thing was put in a hateful context.