Alternatively, imagine someone prone to violence who adopts an ideology that tells them a certain group of people are their kinsmen/friends/allies. Would they not be more likely to control themselves around that group of people?

This seems to be the origin story of David Wood. Dude is a genuine psychopath who attacked his father with a hammer but then found Jesus and became a devout Christian who warns others about the evils of Islam. I still think there's a really important component of religion that gets overlooked in that it imposes an authority figure onto the population that is beyond their reach. It's one thing to overthrow a king, that can be done, it's something else entirely to overthrow the divine.