The courts will not see, and have not seen shunning, as torture. You have the same constitutional right of free association as the Witnesses do. You have the right to leave. They have the right to avoid you like the plague. While it is their religious doctrine, it is also an individual right. Each Witness makes their own decision on what ever basis they choose. You may not like it, but it is their right. There are two constitutional issues here: Freedom of Religious conscience; freedom of association.
By ranting and complaining, you show everyone that it works. You are punished. Why give them the joy? There is always the return smack: "Dear Mom and Dad. You know I love you endlessly. But I cannot associate with you as long as you follow the path of sin. Unkindness to family members is a sin. I pray that you repent."
Another issue is this: Some of the behaviors that lead to disfellowshiping among JW's are horrendous, nasty, nauseating. Who in their right mind would associate with someone like that? No every "case" deserves contiuned family contact. I feel that way about my brother, now long gone out of the "truth." Good judgement - not religion - tells me that any contact with him would be like stepping in vomit. And you want a law that says I must be kind to a man who is a sore on the butt of humanity?
And how would such a law be enforced. Suppose a law forbids organized shunning. Do you think it won't continue? All one has to assert is their personal freedom of association. "But, your honor, I don't want to associate with my uncle. He's a sexual devient who [insert act here]. I don't want my children or myself subjected to his life choices."