Watchtower will say that at your baptism you voluntarily entered into a contract with them to abide by their rules and knowing the consequences that will come to you if you disobey.
They will also say that the decision by family and other JWs to shun you is a personal decision and they cannot force members to associate with anyone. They will say that members are exercising their personal religious convictions when they choose not to associate with you.
I think the best route that can be taken is to use their own literature to show their repeated instructions to members to shun their DFd relatives; and show the penalty that comes to those who refuse to shun DFd ones. You would have to make the case that WT is inciting members to engage in this action rather than the members just coming up with the idea all on their own.
In other words, you would have to use a line of reasoning that is similar to the line of reasoning used to criminalize inciting of hatred toward certain groups. Work on proving that the JW organization and its Governing Body is an extremely influential authority in the lives of JWs and couple this with their instructions to JWs to shun former members.
But it will be hard because religion is involved and states tend to be very wary of doing anything that may be seen by some as trampling on religious freedom. They will tend to err on the side of having your personal rights trampled on than doing anything that can be argued as violating religious freedom.