NRO Comments on the Shooting

Mackubin Thomas Owens and
Jack Dunphy on National Review explaining the actions of the soldier who shot the wounded Iraqi. In both cases, they make the point that the soldier was justified in assuming, based on past experience, that the insurgent was faking it in order to get to attack him.
But both avoid the trap that Hack Kelly falls into by stating definitively that the insurgent was "feinting death."
(I don't have the references right now, but I recall reading or hearing reports that definitively identify this man as an insurgent rather than a civilian, so I am now comfortable definitively calling him an insurgent).

Michael Ledeen, on the other hand, offers something that I'm not certain I understand. He points out that a certain British soldier, by the name of Henry Tandey, could have killed Adolph Hitler way back in World War I, and by sparing his life, allowed him to take over Germany.
I am not entirely certain what the point is here.
In all due fairness, this was an excerpt from his book Machiavelli and Modern Leadership, and contains no commentary except for the passage in the book, so it doesn't comment per se on the current issue of the Marine shooting the wounded Iraqi. moreover, it is not clear whether Mr. Ledeen chose to put this comment on NRO, or whether it was the editors.
Nonetheless, in the context of the current situation, what is Mr. Ledeen's point? That we should never take prisoners but kill everyone associated with the insurgency? That we should kill anyone that we suspect might become Hitler in the future? I'm not certain I get it.
In any case, I am troubled by the idea, implied by the article, that we should think about preventively killing anyone who might become Hitler in the future.