Decorum is about shame.
Manners are about shame.
Respect for parents, family and friends is about shame- and these are all good things which encourage good behavior.
I could on and on, but if Lanza had considered what he wanted to do would shame and humiliate his family forever, he might not have done it.
When I was a kid, I had an opportunity to cheat on some exam in school. I didn’t out of fear I might get busted and humiliate my parents.