This is a question that comes up a lot when discussing the problem of evil, and it is a fair one. If anyone else had the power to prevent an evil, and then declined to do so, we would rightly view that as evil. Wouldn’t the same apply to God? I think the problem lies in free will, which I know is the standard boilerplate for such things, but hear me out. Many atheists respond that if God is all powerful, he should be able to somehow come up with a way to prevent the evil while simultaneously leaving free will intact. Is this possible? Imagine the following scenario:
A man has a woman cornered in a dark alley, gun in hand. He intends to murder her. Now let’s say that God has the moral obligation to prevent this act, but he has to do so without interfering with free will. How could he do so? Make the bullet miss? By miracle, have the bullet not wound the woman? Make the gun malfunction? Let’s say that one of these happens. What would the gunman’s response be? Anger? Frustration? Both indicate that the gunman had every reason to believe that his actions would be successful, and is now surprised to find himself foiled. Now, if God has the obligation to prevent this occurrence of evil then he has an obligation to prevent every occurrence. Every time someone tries to harm someone else, or lie, or cheat, or what-have-you, something - either miracle or coincidence - will prevent the evil from happening. Don’t you think that humans would figure out pretty quickly that they aren’t actually able to act upon their choice?