Just tell them you’re heated and that you want to take a break in order to breath and calm down. Then come back later and say what you wanna say. And if it’s still difficult, just tell them you stutter and write a note out telling them what you want to say. It actually makes you look pretty tough that you’re controlled enough to walk away, and courageous enough to admit you stutter and to write them a note. Then nobody will be able to make fun of your stuttering because you proactively mentioned it. And you will feel better anyways after leaving a situation to calm down and think about what you really wanna say. It’s about valuing your own time and what works for you (not what they expect you to do). That’s what will give you a sense of dignity.