If your brother is a witness, he no-doubt already has plenty of people meddling in his life. What good could it do to demonstrate that outsiders can be as petty and childish as the JWs?
Just let it go and hope your brother sees the light. Take comfort that somewhere in a stadium once your brother enjoyed a normal human experience. Don't let the evil things he does in the name of religion justify doing evil things yourself.
- Lime