If this an American university, take it up with your student affairs department and talk to someone from the office of disability services regarding accommodations. Your professor is not qualified to determine whether stuttering is or isn't a disability so they can fuck right off. That said I agree with others that you should do the presentation. The teacher sounds like an asshole though so I would document this interaction and the conversation with the aforementioned office just in case she tries to mark you down for stuttering during the presentation.