If the logotherapy works: great! No worries! If it doesn't work: Show him that it's okay to stutter, and that his opinion isn't worth less than anyone else's. It can get better with time, but it's not likely. I believe I've been told that a child who stutters after an early age will most likely have it for the rest of their life. That being said it isn't the end of the world. Bullies and comments are inevitable, but teach him that the people who put weight or emphasis on that part of him aren't worth his time.