It is not confusing at all once you understand it, which you clearly don’t as the statement “Your position is intellectually untenable, and morally hypocritical” demonstrates.

Without a comprehensive understand of Natural Law you’re left with trying to do moral calculus on possible events which may or may not occur and no framework in which to assemble them.

Your military training notwithstanding, the other soldier may raise his hands and surrender. You may miss. You may be shot first. A bomb may obliterate both of you.

The morality of the act depends on that which you will, since no one can be held accountable before God for something that he did not intend.

Once you’re in the field, and the other guy has a gun, if you do not defend yourself you will be shot, and perhaps killed.

You were trained to shoot at the chest area because it gave the highest probability of hitting him.