Fuck. I'm so sorry. That sounds terrible, especially for grown ass adults acting like children. I highly recommend you approach the professor later when he's alone and explain your situation. Even if he's a dick, you did your assignment and a fucking speech disability should have no relevance to the grade you earned. It's a pity the world is full of unempathetic manchildren. You'll have to become more durable to bear nonsense from these idiots until you learn to ignore it. It's gonna get better OP. Today must've been rough, but never stop trying.