It didn't get people talking about it, it got people arguing about it.
I don't like Michael Moore's approach because he seeds it with a personal agenda that only encourages divisive argument. And it has - the fracture of American society along political lines hasn't been so pronounced for a very long time.
I don't approve of every policy the American's have undertaken under Bush, and I've said so on these forums. But Moore carries it to far, trying to say "Look, the President is a moron and a crook, therefore we can do no right."
In my mind, a better way to challenge policies would be to present the material in a manner that says "Look, this isn't really the best way to go about things, you are the C-in-C, so see what we have to say". In this manner, you would engage Republicans who are not really keen on the chosen path as well, creating a much stronger piece of political commentary.
But he didn't, and now no-one with real interest in the matter takes him seriously.