Saying "burn n***ers burn" is one of those things that you shouldn't say pretty much anywhere, so I'm not really persuaded by your appeal to ignorance in not reading the incredibly short 6 rules. And someone saying "warning, x is a racist" isn't an invitation to say such a thing, even if you don't know its a joke that the person is racist. Also, I don't quite follow how that'd be an invitation even if it weren't a joke.
