I really believe the GB is sincere, they are convinced that their behavior is what Jehovah has mandated
They also cherry pick out the old Hebraic laws which they can use to support themselves, their doctrines, their power and Judaical penalties, play the ruling judge who makes laws as it were.
The Disfellowshipping policy to name but one.
They essentially turned themselves into the High Priests of the ancient Hebrew civilization.