Saito was evidently seriously wounded and captured during an attack on a truck convoy that he was acting as a security guard for. (
http://www.japantoday.com/e/?content...at=2&id=337300) He wasn't individually targetted and deliberately killed. He was in no way "unwittingly" providing anything to the "coalitioneer's", he knew exactly what he was being paid to do. He was directly supporting the invaders, therefore he was either a legitimate target, or else he was collateral damage, something you don't seem to mind when it's Iraqi civilians that are casualties.
According to your rules, individual citizens aren't allowed to do anything to defend their country. It's a great advantage to be able to make all the definitions, everyone that doesn't fight exactly as we demand is simply a terrorist.