it's funny.
it's not simply people who "Wear their racial friendships on their sleeves", it's about racist jerks who make race the basis of their "Friendship". You know, "that guy's black/lesbian/puerto rican/in a jagdgeschwader, so I'll be his friend".
It is a joke, and Animal's right, it's a joke better appreciated by blacks than whites.
And sure, animal, I'd love to live in a world where nobody gave a damn about race. But I can't, and so I have to disagree. Racism is pervasive in our society, and it affects everyone (hence the hangman "racism" joke). I mean, it's simple: we've been conditioned to see say blacks differently from caucasians. That doesn't mean we have to make judgments based on that, but that's how we process the information. And yes, people do feel that different reaction in body language. That's racism, and everybody (including members of the so-called minorities) has to work actively against it.
That doesn't mean giving racial stereotypes a positive connotation.