I'm no apologist for JWs and (I was bought up by JWs but never got baptised and never subscribed to their beliefs) I was one of those who argued that they should be free to practice their religion. It is an adult's right to belong to any crazy cult they like. I don't think it is the business of government to dictate to people which bunch of religious nutters that people are allowed to join.
If individual JWs have broken the law they should be held to account by a court. Similarly the JWs rules on reporting child abuse falls woefully short of the standards that we expect and I think the courts should force them to correct them, banning them would not improve the situation for children being bought up by JW parents in any way.