Lawdog,
In feudal Japan prior to the 1868 Meiji Restoration, a samurai could kill any impolite person who was not samurai or noble with no penalty. Also, many if not most societies as some point in their history did not consider the killing of any non-member to be murder. The names many cultures had for themselves translated literally as "The People" or "The Humans" while their name for foreigners literally translated meant "Not People" or "Not human."
Be that as it may, all of which still had the concept of 'murder', and each society understood 'murder' to be wrong, however they defined it.
In the example of the samurai, they had to justify the killing on a point of honour, or courtesy -- otherwise it would have been murder.
The cultures which did not consider the killing of a non-member to be murder, considered the unjustifiable killing of a member to be murder.
They still have a concept of 'murder' and part and parcel of that concept is that it is wrong.
LawDog