Captain Kirk - As I said, I know the circumstances of the Apache video. The Apache was not alone - he had topcover from more than just one other aircraft.
The Geneva Convention link really was just a link. I wonder if it applies - there are so many ways to interpret it and I am not a lawyer.
That said, following the ideals of the conventions should be the norm. There are no black-and-white situations (otherwise this would be easy) but I suggest that it is much harder to apply the conventions when storming a machinegun post on an enemy held hilltop than when sat in several million dollars of the most deadly equipment on the battlefied watching a man with no legs crawl away from you.
So where do we draw the line? I guess that's down to the individual at the time and the subsequent board of enquiry afterwards. That's why, as BEagle said, "Troops of any nation need to be suitably trained and have sufficient discipline to make the right judgements instinctively".
No offence taken, btw
