They are all about hierarchy and obedience.

Falling out of any norm is an act of disobedience.
You have to be like us to belong to us.
You have to look like us to be like us.
You can't have anything unique to look like us.

Brightly colored hair, tattoos, piercings, non-conformist clothing show that you don't submit an show disobedience.

This is improper.
So you are improper.
Probably dangerous.
Keep away from people like that. You don't wanna be like those.