Well, you're kind of cheating a bit there since murder is by definition any killing that is wrong. But I think you'll find HUGE differences in the standards that different cultures use to judge when it is or isn't acceptable to kill people. There are some cultures where it's never acceptable to kill anyone for any reason, even in self defense. There have benn other cultures where you're perfectly justified in killing someone simply because they insulted you. So far as I can tell, Norsefire is simply confused about how atheists are able to behave themselves even though they aren't under constant threat of magical punishment.