Hello! I am so sorry that you are experiencing this. When I was in undergrad, I had to present in one of my classes. I met with the professor before hand about the presentation to set some expectations. I thought things were good. After my presentation, I received a grade much lower than anticipated. The comments attached stated that my stuttering conveyed a lack of comprehension of the material and that points were taken off due to going over the alloted time. I ended up having to go to the disability advocacy office to file a formal complaint. Please dont feel bad formally filing a complaint. Your professor is perpetuating the idea that your words have less weight than anyone else's, and they DON'T.