the "higher standard" that BYU has claimed doesn't preclude defending yourself and your friends when someone starts punching and swinging helmets at you. Never really found that in the honor code anywhere...
I think "common decency" as you call it would actually call FOR defending your teammates.
The exception, in my opinion, is Kai Nacua. But even then, I don't pretend to know what happened before the onscreen sucker punch.