I'm trying to view this objectively which is difficult particularly under current recent circumstances.
I cannot even begin to imagine being in any sort of theatre at war, knowing that there are any number of soldiers and insurgents trying to find me and kill me. So I can only form an objective view with a subjective mind!
I think on the one hand, what he did was wrong. The man he killed was injured and I understand that he ordered him to be dragged out of the way of the camera on a balloon, refused him first aid and shot him in the chest. Looking at that from the comfort of my conservatory that seems wholly wrong to me since the man was not a threat having already been injured by fire from Apache helicopters. And then you add in the conditions that he was undoubtedly facing - a gun fight with all manner of weaponry being deployed against you and colleagues either dying or in danger and one cannot begin to imagine the emotional and mental trauma he was facing. Hence, no doubt, the finding of diminished responsibility.
However, I cannot help wondering that were we in a reverse situation where the Afghan fighter had dragged an injured British soldier into the bush, denied him medical aid and then shot him whether that Afghan soldier would be treated in a similarly sympathetic manner.