American physicist and Nobel winner Steven Weinberg has famously said, "Religion is an insult to human dignity. With or without it you would have good people doing good things and evil people doing evil things. But for good people to do evil things, that takes religion."
But where does the atheist and naturalist find objective values of good and evil in his worldview to make this judgment? There are no good or evil people; there are no good or evil acts. His worldview doesn't support this judgment. All he can do is report what he does and doesn't like, personal tastes about religion and behavior.
The atheist must 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.
Greg explains more here.