Yeah, there's certainly levels of shunning. There are plenty of people in the world that I'd just as soon avoid. A lot of folks are just trouble looking for a place to happen. No sense being near 'em when it does. Live and let live in those cases. <shrug>
But that is a considerably different thing from active shunning, the kind that I'd consider morally equivalent to force. That's where you go out of your way to mentally make the person non-existent. You are not just expressing dislike, you are attempting to deny their very presence. It can be DAMNED effective if a bunch of people start doing that to somebody. I've seen several people quit good jobs and move to different towns because of that sort of treatment. And in two extreme cases I've witnessed they tried to tough it out, and cracked under the strain.
I didn't know either of them well, but I'd hazard a guess that they must not have had a very good support network outside the work/social circles this was happening in. We all to a degree deal with similar psychological pressures day-to-day, living among a vast population of statists who either passively or actively disapprove of our ideas. Hell, my family thinks I'm nuts half the time, and we're pretty close-knit. I know people who have pretty much stopped speaking with their family because of their embrace the freedom philosophy. One of the big things the 'net has done for us and a lot of other "splinter" social groups is given us the means to find each other, and gain an extended network to support themselves against those day-to-day pressures.