Royal Marines executed injured man

Marines ‘murdered man live on camera’: Court martial sees graphic footage of ‘execution’ of injured Taliban fighter
The victim was left twitching and gasping for breath as the British servicemen, apprehensive that they might have been spotted, pretended to give him first aid

http://www.independent.co.uk/news/uk/crime/marines-murdered-man-live-on-camera-court-martial-sees-graphic-footage-of-execution-of-injured-taliban-fighter-8899912.html

I know what some will say – he was a Taliban terrorist, they did what was right, let all of them get shot, etc. There, I’ve saved you the bother. Move along, there’s nothing to see.
BUT
Is this the sort of thing the British military is renowned for? Does this not reflect badly on our troops? Will this not cause problems because the Taliban are not complete fools, they do remember?
Had this been done by German troops we would all remember the terrible things the SS did, what happened in the concentration camps, the way the world believed that it was in the national psyche to treat prisoners badly. And it would be the same with Japanese troops as well.

Imagine you were talking to your grandfather
You: what did you do in the war, grandfather?
Grand: I executed an injured man, lad.
You: why?

How would you answer that question?
How would you feel if you were told that by your grandfather or, indeed, any relative?
The British military has had a reputation within Britain for being fair when the fighting is over (elsewhere though, some might remember things differently, like the Kenyan Mau Mau for example, or the Boer part of South Africa who know where concentration camps were first used) so this news reflects badly on our national standing.
Americans, in general, do not believe that the things regarded by others as a breech of military protocol done by their military in the liberation of Iraq and Afghanistan were a bad thing (executions of injured on video, urinating on bodies on video, abusing prisoners to break the boredom for a camera, torture, long term detentions under duress), but these things (and more) are against the human rights agreed by the United Nations, and you cannot pick and choose who you allow to apply those rights to. Ok, so you know that the Taliban do not follow the human rights convention and would execute you in a heartbeat if the tables had been turned – but is that any reason to stoop to their level?

Ok, you discuss.