They didn't have libel / slander laws back in those days.
Laws haven't bothered Watchtower when it wants to practice something. Watchtower just does what it wants under a banner of freedom of religion and asserts it as a theological position untouchable by courts in lands that embrace religious freedom as an inalienable right.
Watchtower does this with military induction. If a JW wants to join the military Watchtower has local elders treat the person as disassociated. But at least everyone knows why the person is, in effect, disfellowshipped. Watchtower does the exact same thing with JWs who conscientiously accept transfusion of blood.
If Watchtower wanted to do this with other "sins" it could. But it does not want to enable this level of transparency across the board because it would let elders reveal to everyone that Johnny disassociated because he was demanding answers to questions that deserved answers.
And, by the way, the slander/libel law in ancient times was that community leadership would stone you to death if they didn't like what you were saying.