I don't really understand the point of shunning. It can't be about preserving the purity of the fellowship (or whatever the correct word is), because the shunned person is still part of it, aren't they?
Is it just to be mean then, like when someone is pouting and they give you "the silent treatment" to make you feel bad? If they wanted to fix whatever the problem was, I would think they would do the opposite of shunning - they would surround you and pay a lot of attention and try to get you back to being the way they would like you to be.
I honestly don't get it. What am I missing?