From time to time, "The Daily Show's" Jon Stewart pays a visit to Fox News programs, perhaps to prove that he's not afraid to back up his jokes. This weekend he stopped by Fox News Sunday with Chris Wallace. The conversation started off pleasantly enough, and then became contentious. At one point Stewart called Wallace "insane."

"I'm not an activist," Stewart told Wallace. "I'm a comedian. And my comedy is informed by ideology, there's no question about that. But I'm not an ideologue."

During...