I agree that killing random members of the congregation of a Muslim preacher whose sermons one doesn't like is inappropriate.
The proposition was not that one did not like his sermons, but that he hints that members of his congregation might kill you if you do not do what he wants - an alarmingly common practice which everyone piously pretends does not happen.
But, on the other hand, in a war like World War II, one has to be willing to shut down the factories of the enemy that are making airplanes and tanks and the like, unless one is not serious about winning.
But, increasingly, we face a situation where the main participants in wars are quasi state, microstate, or non state, where the entities fighting wars are franchises more than they are cohesive states, or even cohesive gangs.
Indeed, state to state war is something of an anomaly. The British empire was not conquered by the British government. From 800AD to 1250 or so, the reconquista was rarely fought by states. Non state wars were normal before 1830, and the present situation is a return to normality. The distinction between war, piracy, privateering, extortion, and brigandage, always somewhat artificial, is once again dissolving.
When we're not yet in a total war situation, however, strenuous efforts to avoid collateral damage are germane to the struggle - because, after all, the Cold War was also a propaganda war, and this is still currently applicable as well.
Observe that Muslim and communist regimes usually kill suspected enemies, potential enemies, suspected potential enemies, and family of suspected potential enemies, and it seems to work fine for them. Everyone loves them twice as much the more innocents they kill. American university history courses treat Sihanouk as a saint.
Similarly, the guys who conquered the British empire were the greatest experts on efficient warfare, since they made war for a profit, and they routinely used collective reprisals, killing an entire village for an offense by a single individual in that village. The people who were most pissed off by this practice, were generally killed by it.
But if we repeat the policy of supporting our own puppet regimes that are gratuitously cruel to the ordinary people, we will rightly earn hatred.
Again, observe that the pre 1830 British colonialists were a bunch of pirates and brigands, and everyone loved them. Obviously they were not
gratuitously cruel, but they were plenty cruel when necessary.