Anger and the desire to do something are common reactions. Also if the local elders have behaved despicably and interfered with family ties then the stress is enough to drive anyone to extreme action.
The Watchtower society is a very difficult entity to have an impact on. They have groomed their members on how to feel and react to any threats so it is difficult to make an impression. What is important is that someone takes time to heal themselves and gain mental strength after an exit from the organisation. Launching any affirmative action whilst stressed and emotional may lead to someone behaving irrationally. This man is doing what he feels is right and is likely fueled by anger and a sense of injustice.
Is anything he is doing illegal? If so it will not be long until the police are involved. He may need to contact ICSA who can put him in touch with counsellors that help people exiting cults with counselling and advice.