For Calvin, all it takes for him to consider becoming an atheist is for God not to give him snow (so he can miss school). I doubt anyone who has become an atheist (or a Christian, for that matter) has done so out of purely logical considerations. Disappointments can lead one either into a life of faith or unbelief.
The God of the Bible will be no one’s genie. He does not send snow when we demand it, nor answer our prayers as we would prefer. Life is filled with forks in the road which lead us either to unbelief or to confident faith. When we don’t choose the latter, we should throw a Calvin-like temper tantrum — at ourselves!