Bill O'Reilly earned himself a new nickname with his latest appearance on 'Late Show' (Weeknights, 11:35PM ET on CBS). David Letterman proposed the notion that America turned Iraq into a hotbed of terrorism that it wasn't before our invasion.

Then, in a move that clearly surprised him, O'Reilly essentially agreed with him that our going in was a mistake. He supported it initially based on claims there were weapons of mass destruction there, which turned out to be false.

Letterman then decided to seal their moment of agreement with a high five, which O'Reilly was not inclined to do. At one point, he even chastised Letterman. "We're having a good conversation. Sit down," he ordered.

But Letterman stood defiant until finally O'Reilly acquiesced and gave him the high five. "No wonder Cheney won't come on your show," Letterman grumbled. "Mr. Grouch!"