There are times when, sick as it is, it is necessary to exectute or disable a prisoner. It's hard to tell about that article, since you don't really have all the facts. Inferring what you can, though, that person has no place in the military.
A team's completion of a mission and survivability largely include rational thought. That also includes NOT doing things your are emotionally driven to do. The execution of a prisoner, unless it is necessarry for mission completion, tells you a few things about the soldier. He is either controlled by emotion, doesn't understand the value of human life, or is a psychopath. Today's wars are about public opinion as much as they are about killing the enemy. A favorable outcome to the war, publicly and militarily, as well as the safety of your team, rely on someone that follows orders without thinking, keeps his head, and respects every life he takes.
