I've been in your shoes when I was younger. I acted in anger. I will say it reduced bullying. Long term I realized that was not the healthy way for me to deal with it and was probably detrimental to my growth. I wont/ i cant tell you what the right reaction is. What I will say is, you need to give it thought and most importantly realize reacting in anger is not your only option. For me, i thought that was the only option. Other ways to deal with it, 1. Try to address your fear of stuttering in the moment and tell him off in a more calm, constructive manner. 2. Bullys like reaction. Do not react to it. 3. It's ok to ask for help. Maybe go to someone authoritative to help address this Like I said, it's your decision what you do. Just know you dont have to peg yourself in a corner by feeling that there is only one way to react.