There are two separate (yet related) issues being discussed and at times conflated/confused:
1. The public comments made by CDS.
2. The rights/wrongs of Marine A's conviction.
The comments made by CDS appear to me to be in response to those made by a variety of media outlets, ex-serving senior officers and the usual talking heads. I'm not suggesting that the topic is off limits for debate, far from it, they have every right to comment and engage in a debate. CDS appears to have been exercising the right of reply as the professional head of the Armed Services in order to address some of the issues raised by some less than well-informed comment.
As for Marine A, I wasn't at the CM so can only offer a judgement based on a careful reading of the media reportage - guilty as charged. The attitude of the insurgents to the Geneva Conventions, their actions or their status as combatants is irrelevant. It is our actions that are of importance (and which distinguish us as a disciplined military force) and his actions were legally and morally wrong. Talk of the fog of war, adreneline, unit losses, 5 months into the tour etc, whilst offering context, in no way excuse the murder of an individual who was no longer a threat.
Having served in close combat roles in Afghanistan for extended periods (I was in Helmand at the time of the incident) I fully undertand and appreciate both the specific and wider contexts within which the incident took place but I cannot accept that there is any justification for Marine A's complete failure of judgement, leadership and loss of moral compass. LOAC and ROE are meat and drink to a professional such as him (especially so as a highly-experienced SNCO) and his comments after the fact ref the Geneva Convention suggest that he knew exactly what he was doing. Murder is murder and I am personally and professionally disgusted by his actions.
MB