All this assumes people living beneath these unmanned multi-ton projectiles are good with no one onboard, or no one onboard being in command of the aircraft. This should ONLY be the case in an actual war zone.
Nautical matters would never countenance such a thing (lack of a Captain) unless the craft has been dispatched in anger (e.g. torpedo). And watercraft can't come get you as you sit in your bed or at work or school.
Unless constrained on rails or in a tube or vertical shaft, a transportation vehicle HAS to have someone onboard to be legally responsible for its operation. Current and future technological advances aside, there has always been, and I believe will continue to be that legal requirement.
Only an operator whose life and limb is committed could really be held responsible. And I wouldn't want ANY large unmanned equipment over my head, EVER!