Because that is the only religon that tells it's believers they must witness and recruit in order to be good christians.
"If athiests hate religion, then that means that ATHIESTS SUPPORT THE HOLOCAUST. Think about that u oblivious ignorant liberals."
You do know Hitler was a devout Catholic, right? And catholicism is the largest branch of christianity.
Also, calling someone a liberal is not an insult. Go read a book.