I don't know if you've heard of this cult called the JW's Nathan Natas? They remove free will from people by coercion techniques that affect all aspects of their lives, even when it comes to family relationships.
Agnosticnow's very valid concern is that this sick method of controlling people will take his child from him. If I was in their position I would also be looking at all avenues of countering the indoctrination with the hope of maintaining my relationship with my child.