I saw a bit of that video. It was pretty interesting. O'Reilly's views are totally nonsensical but at least he's able to argue them like a respectful human being. I'd say Letterman did pretty good up until the '60% of everything you say is crap' line out of nowhere, that just showed he couldn't keep it together.
Plus watching two mild mannered gents having an eerily polite discussion can be damn trippy when your really stoned.