Curiously, at least a few cases of killing your own officer are recorded when it's in your own immediate interest.

http://en.wikipedia.org/wiki/Fragging

I suppose the soldiers asked to do bad things (like this man) rationalize it away.

Well fragging was common on the front lines because it had plausible deniability of the enemy throwing a grenade back. In a prison camp far away from the front, it's more difficult to explain, and harder to get away with.