I suspect it's because atheists refuse to pretend along with them that magical beings and realms exist. They can at least commiserate with other religions that play the god game.
Uncle Fester
Favorite Answer
I don't like sport. No, that is wrong, I like playing sport but watching it leaves me cold. Several times over the years I have been present when fans have been arguing about the merits of their particular team. Then the inevitable happens "So, which team do you support?"......."Uh, I don't, I think it is all a macho tribal warfare substitute." All of a sudden their argument is forgotten and my parentage, sexuality and patriotism is questioned. It is like that, thinking something they hold dear is unimportant is in a way questioning the whole reason d'etre of it and enough to bring them together to attack that which will not play the game. Just as you suggest.
Doug Catholic
Most all other religions contain at least some small semblance of divine truth, while atheism constitutes a denial of all divine truth.
Anonymous
Because atheists are the embodiment of their own doubt that a god exists and what they wish to silence.
Misty
We terrify them more than any other group.
Anonymous
I agree, you're using "atheist logic," which is to say your initial claim is untrue. Christians aren't accommodating of religions that don't worship the one true God, and that includes Atheism.