It was a mock PBS Frontline report with a dead pan reporter who goes in search of Clayton Bigsby, a renowned author of books on white supremacy.
When the reporter makes his way to Bigsby's home, he finds that Bigsby is actually black! The gimmick is that he's blind, so he doesn't know he's black. He was raised at an all-white orphanage and taught to be racist.
The rest of the skit has Bigsby and the reporter going to different meetings of the KKK and book signings as they encounter situations designed to highlight the irony. For example, they are at a stoplighht and there is a car next to them with three or four white teenagers, dressed up in what you might call urban gear, listening to rap music.
Bigsby leans out the window and yells at them to turn the "jungle music" down, "G__damn nig ___s," he mutters under his breath (not realizing of course that he is black). The kids in the car look at each other and one asks, "Did he just call us nig___s?" After a pause, they all high five each other, excited that a black man called them that.
It is with sort of hard to describe. But it is genuinely one of the funniest damn things I have ever seen in my life. And it is so precisely because it is making fun of the stereotype itself by joking within it.