The teacher sounds like a twat! If I may suggest looking into getting legal protection for your stutter, especially if you're in the US. A Lot of people simply just don't care because they cannot understand how having a stutter can truly affect your life. I just don't want to tell people like this that I have had years of speech therapy from license speech therapy! Your little EGO intervention is not going to be what helps me. So respectfully stay in your lane or experience the ramifications of being sued for discrimination. Just because they can't see your disability doesn't mean that it doesn't affect your life. I have lost and been passed for jobs and opportunities because of it. Stuttering is not a joke people insensitively make it out to be. I am tired of it myself honestly!