I think their bullying ways are despicable. On the other hand, demanding that a young person be kicked out of the house could be reframed positively:
The organization cares so much about that young man and they know how unhappy he would be as a witness. So, they are giving him a wonderful opportunity to break free and make his own way in life.
Is age eighteen old enough to leave or be booted out of home? Yes. I would argue that age 18 is far too young to make a decision to commit to the Watchtower Society. I hope the young man makes the most of his imposed freedom. What an opportunity to develop the ability to look after oneself. Thank you Watchtower for protecting this young man from your mean-spirited environment!