I believe the Watchtower can say all that was quoted earlier because they will just say the witness has decided themselves not to be a witness any more. So the Watchtower are not taking anything away or taking any action. They will simply say that the individual agreed to accept all the Watchtower doctrines at his or her baptism. If they later decide they dont want to any more, then that is their decision.
Very crafty of course but its hard to argue against that.