Let us imagine a residential building with about 100 people living there, and let us imagine that there is information that some enemy combatants are living among them. A decision is made to strike at the building in order to eliminate the combatants. Consider two different approaches:
1) An air strike at the building, destroying it and killing most of its inhabitants, and leaving a minority of them wounded.
2) A squad of soldiers enters the building and executes most of the inhabitants at close range, and wounds and leaves alive a minority of them.
Most people would call scenario 2) a deliberate massacre that cannot be justified. Many people would, however, call scenario 1) a legitimate military strategy with unfortunate collateral damage that cannot be avoided. Question is, why? The outcome is the same, but for some reason the impersonality of striking from distance (air strikes, missiles, or artillery fire) seems to make it acceptable in many bystanders' eyes.