If religion were not there, as with the gun, the atrocities that are a result of it and man combined would not be present today.
No, it would either be replaced by a new religion, or they would find some other reason to do what they wanted to do.
This is my problem with the whole religion and gun debate, people continue to savagely attack the branches of the tree by completely ignoring the roots of the problem. Why do people use guns? Do they feel threatend? Why do people steal? Why do some people snap and kill others? Why does somebody need to feel there is something after death? Why do some people (if not all) feel like they need to belong to an idea, instead of the other way around? Why do people use religion?
You're not gonna get anything out of attacking religion or guns, as they are not the cause of the problem. They are only modifiers.