If you ask on what grounds do I accuse rapists of having done wrong, then the authentic answer is that a world with rape displeases me and this is a tool I can use to get society to impose sanctions against it.
Douthat on Secular Morality « Modeled Behavior. Okay — but at this point, don’t you have to continue, “To those who reply that a world with rape pleases them, or does not displease them, I say…”?