Trouble is, he's NOT to be believed. All we know for sure is that he executed the girl. Nothing before or after that is really known. Forensics can verify her execution. The rest could very well be the fantasy world of a psychopath.
Law is law, not morality.
A key part of morality is following laws that do not contradict moral principles. A law to not
kill someone under these circumstances most certainly does NOT contradict any moral principles. Therefore, it is a law that morality dictates should be followed.
Still happily answering to the call-sign Peetza.
The problem, as you so eloquently put it, is choice.
He is no fool who gives what he can not keep to gain what he can not lose.
-Jim Eliott, paraphrasing Philip Henry.