Even though we've advanced in leaps and bounds over the past couple of decades, and much of what religion represents has been exposed as a cover for corruption, greed and much too often sexual assault, Religulous is valuable in the sense that it gives the "other side" equal time.
As Maher points out in the movie, the idea of Santa Claus visiting every house on earth in one evening is ridiculous, but the thought of one man having the capability of controlling the earth and being privy to all our thoughts is widely accepted.
How screwed is that?
I've got an entire category devoted to my struggles with Catholicism. As youngsters, we are groomed to believe that which our parents believe. As adults, it's difficult for many to reach a different conclusion. Many continue to blindly believe without questioning a thing.
As expected, Fred's entry ignited quite the debate in the comments. When one believes in their religion and/or their God, it's a sin to doubt and even the most sensible, rational argument will fall on deaf ears.
This is the argument you simply can't win. It's not even worth having it.