Victor Reppert made an interesting post that raises the issue of reliability of our moral intuitions. Since it is brief, I'll repeat his post here in its entirety:
A common atheist retort: "Would you rape, pillage, and plunder if you did not have the Bible to tell you not to?"The first question it raises in my mind is what kind of statement is this retort from atheists responding to? It seems to be an answer to the common trope from religionists that atheists lack the moral guidance that comes from God, which is often stated as Dostoyevsky's famous line from The Brothers Karamazov: "If God does not exist, everything is permitted." Many religionists take this claim at face value, and assert that atheists are devoid of any morality at all. To such an assertion, a retort like the one Victor cites might be appropriate. But Victor's view is slightly more sophisticated than that. At least he doesn't deny that atheists have some kind of morality. He just denies that the morality of an atheist is a truly worthwhile or effective way of guiding human behavior.
The implication is that this would be a superficial morality. And it would indeed.
Reply: Theists and atheists alike refrain from such acts because conscience tells them that it is wrong. The question is whether they have equally good explanations for why we should suppose that conscience is a reliable guide to truth. - Reppert