The atheist who challenges Christianity by asking how God can exist in a world with evil faces a bigger problem than the theist.
The theist must rise to the challenge, to be sure. But the atheist must also take his turn offering his own explanation, and his task faces a complication the theist does not encounter. He must explain how evil itself could exist in the first place to make room for his complaint. He must account for the objective, transcendent moral standard that has to be in position before moral judgments of any kind can be made.
This difficulty signals an additional problem: The atheist must also solve the problem of good. How can anything ultimately be evil or good in a universe bereft of any standard to make sense of the terms?
Darwin will not rescue the atheist here, because evolution is a materialistic process that can only produce material merchandise. No stirring and recombining of molecules over time will ever cause a moral fact to pop into existence in the immaterial realm. At best, Darwinism might account for behaviors or beliefs that human beings falsely label “moral” because the deception accomplishes some evolutionary purpose. But it is deception, pure and simple. The kind of robust morality necessary to ground the atheist’s complaint about evil is impossible on a materialist take on reality.
No, the atheist has not gotten rid of the problem of evil by rejecting God. He has compounded the problem. The only thing he has gotten rid of is hope.