Religion is a set of beliefs about God. Hinduism is a religion that states there are many Gods. Islam is a religion that states there is one God. Atheism is a religion that states there is no God. All try to convert people to their religion. When you set about trying to convert people to your set of beliefs, how are you any different or less dangerous?
The difference is this:
Christianity - "God says go murder these people because they are bad."
Atheism - "There's not God, so you don't have any justification that those people are 'bad'".
Atheism is LESS dangerous than Christianity.