Nocal is mostly right. ALTHOUGH, the nature of the Chappelle show was that the clips were written and taped then presented to a studio audience -- if the audience didn't react well, they would cut the clip from the show before it aired. It was actually a really good way to do that type of show.
Nonetheless, Comedy Central was willing to give him a lot of room on this and he still backed out, so who even knows what really went on.
I DO doubt that Oprah threatened to kill him though.