I was gonna do a whole joker-esque spiel about society and how ingrained certain gender roles are, with men being seen as more disposable, but then I realized that sarcasm is dead, and I should’ve been in bed an hour ago… so just pretend I said something smart

I think the expectation is that only combatants are killed.

A more modern variation would be “Those who can’t defend themselves”. In a way it still is because they can’t defend themselves and the bad guys can.