This is simply not true, in time of severe distress and survival pressure humans are clearly capable of mass killings. It happened so many times throughout history. For example a famine forces a human group to take over rivals resources or when defending own group against agressive rivals.
Nobody ever said that these murders are arbitrary. They're the opposite of arbitrary. They're coalition-based murders against men in the opposite tribe. Highly targeted and intentional. Not random.
Lookup the definition of murder because its subtly different from the definition of the word kill. You keep substituting those two words as if they are synonyms and they are not.
