Don King can slide. But when its like "yo, who the fuck are you supposed to be?" than you have to put dudes in check and clown them.
I mean, if you're trying to be Denzel from Training Day, or the Fresh Prince of Bel Air, go ahead. But if you're doing the black face in order to be a "black guy" for Halloween, not in order to add to the character of your costume- then I know a few people that would probably get drunk and end up fighting you if you're at their party.
I got to watch a Vietnamese dude push a white kid dressed up like Lil Wayne into a wall and collapse a huge section of the dry wall. That was funny.