It is how war is usually conducted, and perhaps there is a justification for total war if something poses an existential threat. But you need to consider this

It is how war is usually conducted, and perhaps there is a justification for total war if something poses an existential threat. But you need to consider this in the context of actual reality, where nearly all "war" is really a police action taken extrajudicially by ultrapowerful states against guerilla groups or civilian populations in order to ensure the dominance and power of wealthy global interests. Every war in the cold war was like this. The doctrine of the acceptability of mass slaughter of innocents is how the people with weapons have chosen to use them in these non-existential "wars" but that isn't a justification for that choice.