Why would watchtower keep this information for themselves. I can think of a 100 ways how they could use this information against him without harm for them. It's just doesn't make sense,that they have a proof of him being a predator and let him talk about the watchtower,uncovering the dirty secrets of this cult....
Look at the bigger picture, at keeping control. If they publicly executed him for stepping out of line, why would anyone else subsequently trust them and agree to stay in line? They would lose some of their power over millions.
Letting some minion go is a smaller loss for them. Remember, the truth is he is nothing to them. What do they care if he leaves?