Strongly agree with Heights Good.
I am surprised by the hyperbole around what is quite a clear case (he was filmed in the act, and admitting to a breach of the Geneva Convention).
This guy did his job! Would the Taliban fighter have survived?
Sgt Blackman is not God, or a doctor - whether or not the guy would have survived, it wasnt his call to make, a point he was clearly aware of during the act.
Plenty of guys had a hard tour, and many have stress related issues - but they operated under the bounds of international law. That's why the British Forces are respected the world over, and aren't in a peer group with Nigeria.