Is it possible for you to go to a different company? If you do, maybe stating from day 1 that you have an speech impediment would help people to be more aware about how they treat you. It would also help them know that your speech capacity and your intellectual capacity have no correlation whatsoever. People can come from whatever college they want and still be ignorant as fuck. Ignorant is not the one who doesn’t know, but rather the one that is way too comfortable with not knowing. I wouldn’t have a lot of hope for these people to change.