Bill Hicks, yo.
Well, that was precisely the joke. There's a branch of comedic theory that not only espouses the importance of surprise and shock, but also of crossing taboos. It's a fine line, and fine lines tend to alienate large sections of people. But as with the theory behind two-percenter jokes (
http://www.creatingacomic.com/2009/two-percenter-jokes/), those who find humor in it have the added sensation of feeling like they are doing something illegal.