The Problem of Evil goes something like this: There is evil in the world, God is responsible for creating the conditions for that evil and he knew it would occur, and so that conflicts with a commonly argued-for property of his – that he is all-good. There’s more to it, but that’s it in an eggshell. And I find it pretty convincing. There is a clear logical contradiction between the characteristics theists claim God has and what we actually see in real life. However, I often find people using this as an argument against the existence of any god. To me, they are in clear error. There is nothing which says a god must be maximally good or all-knowing or all-powerful. It could simply be that some powerful douchebag created everything and that’s all there is to it. This probably wouldn’t be a satisfying god for most believers because he doesn’t fit their all-too-common comfort-seeking, but there isn’t necessarily a good philosophical or scientific argument against such a being.
So, use the Problem of Evil against the Christian God and any other God with similar characteristics – there is no good rebuttal to it. But let’s stop pretending like this justifies a robust reason for calling one’s self an atheist.