23 years old, severe stutterer for my entire speaking life. You have a great opportunity here to own your stutter and be the better person. (Which it sounds like you already are.) If you don't let it bother you, you'll come out even stronger and ready for other such situations may arise. You may not be able to control this situation, but you CAN control your response to it. Unfortunately, ignorance and insecurity are a stutterers biggest enemy. People who understand stuttering are usually intelligent and grown up enough to not make fun of it. The best thing you can do for yourself at this point is to just be the bigger person. Your stutter offers you an insight into human nature that these insecure little c*nts will never understand.