Bill Maher dared to speak out in favor of agnostics and atheists.
In this country, it is unfashionable, and in leading roles in politics, often in business and almost always socially, outright suicidal to state that you are an atheist.
When the President of the United States declares in a speech that he believes God wants men to be free, and that is what drives his foreign policy decisions, we are in a frightening and dangerous situation.
Maher uses comedy, sometimes reason, and often ridicule to refute the bullshit that so many religions spew out and try to indoctrinate us with. Most of the interviewees are probably sorry they consented, because none of them looked very favorable when he was done with them, or at least when he decided he should fade them out and move on to his next point.
He also used some of the thoughts and concepts out of Zeitgeist to make his points.
I found it an inspiring movie, but then, I am an atheist. I am not sure if a religious person would walk away with the same feelings. Actually, I doubt that many religious persons would go see the movie. Sorry, Maher, but you have just limited your audience to only 16% of the US population.