From Atheist Revolution:

Whenever someone commits a horrible crime and then claims that some god told them to do it, believers and non-believers unite to reject the claim. Non-believers have an easy time rejecting the "god make me do it" defense because we reason that mythical beings cannot influence human behavior. We might accept the possibility that the criminal's belief contributed to the action, or we might look for mental illness. The believer often has a different path to the same conclusion. For the believer, god did not command them to engage in the despicable act because god would never do such a terrible thing. Of course, one only has to read the Christian bible or listen to Pat Robertson to realize that this is simply not true.