For the record, Howard Dean is no more a "screamer" than any of us would be when addressing a screaming crowd and trying to be heard over it.

That doctored video thing was debunked by CBS (IIRC) back in 2004, showing that the noise of the crowd had been filtered out by using a mic that picked up only Dean's voice.
You'd sound like a raging maniac too, if you were cheering your team at the Superbowl and someone video'd it removing all sounds but your "screams."    :)
Whatever else you think of Howard Dean, that "screamer" thing is a bum rap.