" Jehovah’s Witnesses have been subjected to public censure by Watchtower appointed men acting under Watchtower policy, and Watchtower’s right to continue this policy has been upheld over and over again when taken before US courts.
The threshold at which Watchtower gains this right is at the moment of membership in its religious organization. "
Yes, but nowhere in the cases that you refer to in the first paragraph above does it make the connection to a threshold that you make in the second paragraph in the above quote. The leading case, the one that is always referred to in lower courts when discussing the legality of shunning, is Paul v. Watchtower. I have read the case, and I am curious to know where you think it (or the other cases referred to) makes the connection to baptism being a threshold. As far as I can tell, the statement that "The threshold at which Watchtower gains this right is at the moment of membership in its religious organization" is entirely your own.
In fact, the Paul case said that:
" Providing the Church with a defense to tort is particularly appropriate here because Paul is a former Church member. Courts generally do not scrutinize closely the relationship among members (or former members) of a church."
Note that it said "particularly appropriate" because she was a member, which indicates that being a member is not what the legality of shunning turns upon. That is after the longer discussion that showed the Watchtower would be able to shun no matter what. As the court said, they don't really look at the membership structure or requirements within a church.
Paul case available here