I really don't care about his beliefs or lack thereof, but if he's as overzealous as you say then I'll lose a lot of respect for him. It's one thing to be confident in your opinions; it's quite another to completely trash anyone who happens to disagree with you.
Unfortunately, as you say in Hollywood this seems to be the majority opinion -- I'm not just talking about atheism, which again I have no problem with, but the militant anti-religious bias seems to be a widespread attitude. It does disappoint me to hear my favorite actors saying things that indicate they have no respect for me as a person, even though we've never met, just because of my beliefs. I try not to let it affect my enjoyment of their work, though.