The problem is that many, perhaps most Moslems applaud and support Bin Laden and his goals. They may not strap on a bomb themselves, but the ululating hag celebrating 9/11 in Gaza was not unrepresentative.
Yeah, a billion people can all be wrong. That many were wrong to follow Mao and the Gang of Four. Just because Islam is a religion and not purely a political movement doesn't mean it can't be as illegitimate and murdurous as Mao, Stalin, or Hitler's cults.