Don't allow people to run all over you, don't allow them to disrespect you. Reading this made my blood boil. So what if you stutter? He shouldn't be speaking to you like that. I don't know if it's just me but I would have forgotten that I stuttered and went off on the dude. Send him an email and explain you have a disability and the words did not come out. If he doesn't respond, escalate this up the chain of command, this professor needs to do a better job.