Isn't war strange.
There were many thousands of people in WW2 who repeatedly carpet bombed cities full of defenceless civilians. This was considered acceptable.
Shooting at defenceless enemy combatants was not considered acceptable.
I would also suggest that the Iraqis planting an IED who get a JDAM on the head are just as defenceless as a bloke in the water.
Rules and war are a silly mixture.