The problem with that is that they are saying that if you do not believe in a Christian God that you are then an Atheist. There are plenty of religions that don't believe that God controls men, but that God is a creator. There are also a lot of "religions" that become more of a philosophy of how to live versus if there is a heaven or hell, and there are many religions that believe in many Gods and many ways that a soul lives on.
I am far from being Christian, but I am also not atheist. I lean toward being agnostic, but my beliefs are more Buddhist with a Transcendentalist twist. However, if I were to answer them from a more Christian standpoint, I would say:
God created man with the knowledge of right and wrong. He created a book that teaches them how to behave. He told them to believe in Him. When they ignore him (such as kids ignore their parents) he can not control the evil that they cause. But, by faith in him, you will leave this testing ground we call "Earth" and transcend to pure peace after death. Earth was never meant to be rid of evil. Your life is made to learn and accept God, not to be void of evil. How would you know what good was without evil?
But, in the end, if you have pure faith in you Christianity, nothing they say can change your view. And, if they truly are Atheist, you won't change their mind, either. Atheists are not "devil worshipers" any more than Christians are. They just totally believe that there is no, and has never been, God. It's really a religion all in it's own, because they are believing in something that they can't prove any more than you can prove there is a God.