You know, you're right. I've made comments about this here on FR several times.
Whenever a religious themed thread is posted, the atheists here flock to it. You'd think that since they have no belief in God, they wouldn't pay it any attention, right? I mean, why take the time to type responses about something in which they profess no belief? I wouldn't waste time posting about the tooth fairy.
My honest opinion is that they have to convince themselves daily that God doesn't exist. Just my opinion, of course.
This is good insight. Personally, I think atheists are personally terrified of God. That, and, as it says in the Gospel of John, "men loved darkness more than light."