"If you don't see any difference between someone targeting civilians (and accepting that among them may be e.g. soldiers on leave) and someone targeting military targets (and accepting that there will be civilian dead..." Collateral damage as Timothy McVeigh argued, trying to put himself in the latter category.

It's a very slippery distinction. When you know that most of the people you kill are going to be civilians, arguments saying that this is an unwanted side-effect are hard to credit. And in practice the civilian deaths have always been used as a way of bringing pressure to bear on the enemy.