Advice for a parent of a child with a stutter

Advice for a parent of a child with a stutter I have a 9 year old son with a stutter and tourettes. Every so often someone will say something or mock him. He does well although he does get upset, especially if it's his classmates at school. I am really struggling with the anger I feel when this happens though. The absolute rage I feel when someone mocks him is not going to be helpful to him. I don't act on this anger at all, I might speak to the school or a parent but I do it when I have calmed down but how do people cope with this constantly happening. I can't protect him from it and I don't know how to teach him to deal with it. My heart breaks for him everytime someone does this. I'm hoping for some advice on ways to prepare him, ways to change my outlook or to find out if everyone just feels this rage every time? If you are someone with a stutter what did your parents do that was helpful? Or what do you wish they had done? Thanks