Murder outside the group is most definitely viewed as murder. Perhaps I am not understanding your meaning?
Perhaps someone should have told ancient Israel as they set about genocide---and current Christians as they call for war. It's all relative---always has been, always will be---to pretend otherwise is just silly.
In every group, the penalty for killing someone within the group (and of course these boundaries can be changed. Take capital punishment---this is carried out against someone who has been removed from the group) carries a heavier penalty than killing someone within the group.
Take the Canaanites. They pretty much had done nothing to the ancient Israelites. Oh, except populate a land they wanted. Therefore, while it would have been wrong for Isrealites to kill children, babies, pregnant women, teenagers, men of their own, it became paramount and obediance to their god to destroy every living person in the land they wanted. But I know you only accept certain portions of the bible, and you dismiss this. However, the point is not whether or not this is true, but that people believe it is true, and believing makes religion.
At least a non-believer can be honest and say that morality is relative. If we do something horrible, we have only ourselves to blame, and cannot hide behind theocracy.
NC