You don't have to ban an entire religion to punish harmful behavior.
Shunning, although extremely mentally anguishing for many of us, should never be banned or outlawed. I pick and choose who I associate with. And if I decide I can't stand someone, I shun them. Cut them off completely. I have done that with certain toxic family members myself, regardless of religion.
You can make a law that does not allow people to refuse lifesaving medical treatment (blood transfusions) for religious reasons. This is borderline fascist, in my opinion, but it is preferable to banning an entire belief system from worshipping in freedom.
You can make a law that requires all child abuse allegations, regardless of the number of witnesses, to be reported to police for investigation. And if people violate that law, they can serve Jail time. Again, banning an entire belief system is overkill for this issue.
If you feel proselytizing is extremism, you can ban certain activities. No door to door canvassing. No street witnessing. Enforce the law with stiff fines. JWs aren't rich and they'll soon find other ways to get their time in other than public evangelizing.
again, you don't ban an entire belief system. You legislate consequences for the harmful conduct.
It's really quite simple: if you support the ban, you are LITERALLY supporting fascism. You escaped a fascist authoritarian organization only to support fascist authoritarian governmental actions.