https://www.econlib.org/jus-in-bello/
This rather butchers the principle of proportionality in the laws of war too. It is about balancing the expected incidental harm to civilians in relation to the expected "concrete and direct military advantage". Hamas using civilians as human shields is a war crime in itself, but they don't suddenly stop being civilians as a result.
The US and other countries do have non-combatant casualty values (NCVs) that vary based on the target. These can be as low as 0 or the single digits. But even with these values, civilian harm is to be avoided or minimized. It isn't as simple as this framing.
May I suggest this friend is a ghoul.