It almost seems easy to some... or like a weird funny feeling like they are doing something wrong if they go against something inside of them and actually speak to marked (people they are told to shun) people.
(sorry to be bias in this but only exaggerate circumstances to make my point)
Jehovah's witness for one are known to shun disfellowshipped members.
But also there is:
Popular kids at schools who shun unpopular kids at school.
Rich people who ignore poor people.
Some Whites that are still racest shun black and vs.
Some older proper/religious ones with high moral standards shunn or at least look down one the rebels.
...Seriously does it make life easier for them or something?
What would make them change?
And most importantly when is it right to shun or is it really right at all?