What I've never been able to figure out is this: how much of what he says is real and how much of it is shtick. I think this piece by Ed Driscoll is spot on. Driscoll quotes a reader on Instapundit who described Olbermann thus:
The act is not at all what Olbermann says it is. It’s a very old act: The fire and brimstone preacher.
The left has become horrifically sanctimonious. They have become what they hated in the right back in the 60s.
Every issue for the left is a moral issue on the level of the Vietnam War and the Civil Rights movement. So, their opponents are always wicked devils consumed with sin.
And, it’s their job to save us from eternal damnation.
Olbermann is just the secular version of the fire and brimstone preacher.
Just nowhere near as attractive or moving.
You do get a sense that had Olbermann been born 350 years earlier, he'd have been fully capable of being Jonathan Edwards. Although I'd say Edwards is a lot more fair-minded.