When the Amish shun a person they aren't taking away their ability to survive. They are taking away their ability to socialize. For most humans that is an extremely painful condition. It leads to depression and despair. There will always be some who can handle it better than others. Like any other human trait, it is distributed on a bell curve.
This is the second time you've quoted my disagreement with your post to point out what you meant, but truly I did actually understand the first time I read it. I see the potential effects of shunning differently to how you see them, evidently, and generally was making a point that I think is valid, let's agree to differ.