I'd explain that I don't hate God. I think God exists only within minds. I don't hate Christians. Some of my favorite people are Christians. The only thing I hate is harmful behavior, whether it is carried out by a believer, or by an atheist. I don't even hate the belief in God; it's perfectly fine, and perhaps even good, for some people, but I don't think it's an accurate reflection of reality, and I think it's a source of a lot of problems.