If we want to apply morality to war, we're setting ourselves up for failure from the start.
Morality applies to pretty much all human activity, almost by definition.
Why would you purposefully kill more innocent people when the possibility is around to kill less?
If it is possible - for example - to find out where the terrorists live, fire a Tomahawk missile at said location, kill the terrorists - and, say, fifty innocents - why should we instead pick an option that would also destroy the city they live in?
Happily we have reached a time where guided weapons reduce collateral damage - and simultaneously make friendly troops safer (because rather than deploy, for instance, multiple squadrons of bombers to plow everything around the target into the ground with unguided bombs, exposing the bombers to AA fire in the process, you fire just one or two ALCMs from beyond the horizon) and improve engagement effectiveness.
This is not, mind you, some starry-eyed leftist view that 'if one Pakistani child is killed it is a war crime'. Merely pointing out he calls 'to level the entire city' are at the best merely emoting.