Because shame is healthy. Shame is a necessary component of community's immune system. Because shame bypasses ridiculous word games and shouting matches and communicates "the more you struggle to justify being a horrific person, the less welcome you are here."

The worst thing you can do for someone being truly horrible is act as though it's fine, that love alone will get you through it, that we all just have different opinions and thoughts. Think back to child rearing, the formation of our moral centers.

What was most effective then? Not angry punishments. Not being whipped or slapped. It was disappointing someone whose approval you crave. Someone you love and respect.

Shame isn't only an internal feeling we experience independent of those around us. It's a reflex. Sure, some people just won't have it. But most people? Most people have enough innate reflex that the proper response will illicit shame in them. Exercise it because you love them.