I've read some of the reviews on rottentomatoes.com so far. It's interesting -- even some of the positive ones take him to task on certain things. For one thing, I think a lot of critics, although they may agree with his politics, think Moore is a self-promoting jackass who condescends to the "common people" he claims to champion.
For as much as the left has tried to demonize Rush Limbaugh as being deceitful when it comes to facts and hypocritical when it comes to his private life, the left was far too silent for far too long with regards to Michael Moore's own distortions and hypocrisy (a rich anti-capitalist who made a mint selling anti-Americanism abroad).
Look at Newsmax and go farther in the hyperbole behind claims. Look at Art Bell and go kookier in the claims. Look at Jon Stewart and dumb down the political humor. That is where Michael Moore resides on the landscape. No wonder the intellectual crowd has grown tired of his tirades and see him more of as a liability this election.