The question is not if shunning is harmful or not. The issue is if it's harmful enough to have the government come in and legislate it.
Also, how do we quantify the harm it has caused? There is an untold number of disfellowshipped ones who have returned to JW's and have been the vocal promoters of this policy, given interviews in assemblies and conventions.
I sincerely hope that we are not advocating for setting a precedent that gives the government the power to beat down anyone that it doesn't like. I bet that at some point in the future, we will be on the hurting end of the power we gave to the government.