I have been told by a religious person that, if they were to learn that God did not exist, they would immediately embark upon an orgy of murder and theft, because, "There would be no reason not to." They believe this about themselves despite the fact that we know it to be a misunderstanding of psychology.

To avoid a typical mind fallacy, let's say that some people really have no non-supernatural reason to avoid murder and theft. But they are in a minority, so there is a high prior probability that the given religious person does not belong there.

However, I would love to know that for the given nonzero subset of humanity that has no non-supernatural reason to avoid murder and theft, how effective religion really is at stopping them.