Startrekangel, you make a valid point.
I don't think the issue is 'shunning' per se, but, rather, whether 'official shunning' should be in place.
Of course we all make decisions on who to associate with - it is normal human behavior. And, in so doing, we all shun to some extent. I do. I have many people I have made a personal decision to 'shun' (family members included). It is called 'keeping my environment safe'. And I have the right to do that. Personally.
BUT - does an organization have the right to shun? Or the right to tell its members who to shun?