Atheists, I need help with a real for a statement?

I was talking to one guy after saying how imperfect the world is... And he said, "god made a perfect world. He also gave man free will. All the bad stuff isn't his fault. It is man's. ". That totally took me aback, I've never had a good response. What can I say that will support atheism? Nothing degrading about Christians, I dont want to offend him.