So the "shall not murder" is more of a law meant to protect society, than it is a moral obligation? (Not directed at anyone in particular.)
I wouldn't put it that way. If you look at animals, they might often fight over food, mates, territory or rank, but these fights rarely end fatally when all participants are of the same species. The way I see it, there is an inherent urge to hesitate before anything kills a member of it's own species. This also used to be a thing in war, where you'd have reports of soldiers throwing rocks at each other even though they had their rifles on them. But yes, when you think about it "treat others the way you would like to be treated" is a damn good rule and probably this concept put into words.
