Unexpected unfairness in movies (probable spoilers)

Ah, I looked at it form European theology, where if one type of killing (for money) is wrong (and the intent was only to rob, not to kill, it went bad), then the other type of killing (for revenge) is also wrong.
We don’t share the American attitude that killing for revenge is just, or in accordance with the Bible. Even the Old Testament is a legal code, not self-justice as Sam does.