I dunno, O'Reilly always struck me as a pretty intelligent guy. The problem is that he thinks so too, and it results in his ego and the yes-men at Fox reinforcing his preconceived opinions about everything.
But I have watched his show only a handful of times, and I can remember multiple instances where he's conceded a point, acknowledged the possibility that he's been mistaken, etc. It's rare in a sea of abrupt cut-offs, talking over "guests", and general blowhardism, but it's more than you'll ever get out of Chris Matthews or Sean Hannity.
-J