That's a tired old argument that the only source of morality is the rules laid down by a supernatural creator. It's very creepy to think about because it implies that the only thing preventing the religious people from being murderous raping fiends is their fear of punishment in an afterlife.

Personally I'm with Hans Hermann-Hoppe and his theory of argumentation ethics. Which could be summarized that the act of arguing with someone presupposes that both participants in the argument own themselves. And if that assumption of self ownership exists it also implies that using force to deprive that person of their self-ownership (rape, murder, theft) would not be ethical.