My dad absolutely loves this guy, and I'm a flaming social liberal, but I hate Bill Mahr because he's a lazy comedian. He made a career of pointing out how stupid George Bush was, which frankly takes no skill. After growing up with the worst president in recent history, I don't want to hear about Gee Dubs anymore. Hate Micheal Moore too, he's just fat and obnoxious, enjoy Rachel Maddow though, so cute and smart.
For the record, I don't really put Bill Maher any lower than I'd put any other prominent opinion slinger, conservative or liberal. Rush Limbaugh is also an established personality who has been in the industry for decades, I think he's a douche too (for different reasons).
The atheist comment was something he does that most atheists do that I find annoying, but that's a debate for another time.
I find with Maher that none of his views have been reached rationally, they have no logical underpinning. Even those that I agree with, and there are many, have been reached in the most ridiculous way, the similarities in our views are therefore only coincidence, and bound to happen for that reason alone.
We see this in his shows, and his films. He refuses to engage in rational discourse or have a serious argument, and will change the subject or crack a joke to escape an argumentative pursuit. A lot of this may be put down to the television format, but he also does it in his films where he has the time and creative control to do differently. And he does: without a studio to keep him contained he can simply run away.
He's all right for entertainment purposes, but his views cannot be taken seriously.