Not being a JW a father may not want a son to use druxs or live a amoral lifestyle. The gov protects a person’s right to be free but a parent wants his son to be happy and to be healthy and to prosper. He won’t tolerate conduct that he believes is devastating to his child. The group lives by a moral code and allowing conduct outside the morality harms the offender and the group. The group should not be forced by the gov to tolerate conduct outside beliefs and practices of the group.
And they are not forced to tolerate conduct outside their beliefs and practices. They are even free to shun. As adults.
But the government has a duty to protect minors and social isolation is one of the cruelest things you can do to a social animal.
If the father who wanted his son to stop drugs started beating him with a whip, the government would step in and stop it because it's child abuse. Even if the result was the child stopped drugs.
But all of this is moot because, again for those at the back (Fisherman!) no one is stopping them practising their faith as they see fit . The government has certain criteria that any religion applying for the hand out must adhere too. Freedom to leave without consequences is one and child protection is another. Watchtower simply does not meet that criteria.