I vaguely remember some science fiction short story from the late 60’s about this scenario - two men alone in a missile silo, and the order comes in to fire. No sure, I think one refuses, the other kills him, but the two fire keys are more than 6 feet apart and must be turned simultaneously, so the zealous guy has still failed…
The argument for bombing civilians is that in an industrial society war, almost everyone’s a participant and a target - the person who drives the tank, the one who makes ball bearings so the tank can roll, the one who packs the lunch for the ball bearing maker or paves the road so the bll bearings can be delivered t the tank factory, or runs the generating station that provides power for it all, or farms the food for the soldiers and workers. Seriously where does it stop? There’s a reason that all-out war makes no sense.