We all know this to be true. He's very very silly. His silliness has nothing to do with whether he's right or wrong. I don't know if he's really been right about everything, but he's certainly been right about more important stuff in recent years than most of the people on Tim Russert's rolodex. Still, he's a phenomenally silly person, so silly that when he's covered in the media there's tangible eye rolling by the reporters in the copy.
Since his silliness doesn't have much to do with his judgment on important things, it's worth exploring why he's so silly. As we know, you can be wrong about absolutely everything and still be a Very Serious Person Who Is Not Silly At All. Still, poor Dennis. He's very very silly.
He's silly because he talks outside the bounds of acceptable discourse which have been established by The Serious People. He doesn't try to work within these clear boundaries, but instead steps outside of them.
Howard Dean was also branded a very silly person by the Wise Old Men of Washington. He had the temerity to suggest crazy things which were not supposed to be said - the Iraq war was a bad idea, the capture of Saddam Hussein wouldn't make us safer, etc... etc...