A hint I think may be gathered by the various comments on this thread.
I was quite amazed at the number of people who liked this film who want to make it "mandatory" or "compulsory".
I think this gives us a little bit of insight into the reason this film and the issue underlying it is so polarizing.
The Global Warming issue appeals a lot to people who want to force others to "do right". It appeals particularly to more "liberal" leaning people because it doesn't have to do with bedroom morality which is what usually gets conservatives who want to force you to "be good" going.
And that's the problem with the film. Al Gore is a politician. And a very successful one at that. He just can't help himself from appealing to those people who want to force others to do as they would. The political appeal is just too great.
And there we are left with a scientific issue that may be of huge importance, reduced to a political issue appealing to those in the body politic with a predilection to force other to "do right".
Another interesting question is how did the Environmental movement get hijacked by such people?