It doesn't really matter. Lack of morality in the end because of the lack of good education, decent childhood environment, legit family, nice teachers, etc.. Your dad may be like this exactly because he was often mocked by his grandfather when he was a child. It could also be somehow an innate psychological predisposition due to brain structure. Perhaps it was more difficult for him to empathize with people by nature. Isaac Newton was an extremely mean person, which led to such an extremely intelligent man having no friends and a lonely life. If this is the case, then it is no different from being born with a stutter. It's all just unlucky in some way. Once you understand all this, you will realize that you're not really a victim or weaker person most of the time. Some people value morality, respect others, and on the contrary, some couldn't understand the importance of respect. You already surpass him in this field of education, and he can't even reach the average morality of average reddit users. Every act of disrespect on his part actually maps some form of disconnection from society and from the future. Maybe you can be cured of stuttering. Maybe you'll never be able to converse fluently. But you know how to respect people at a way younger age. You may have better friends who know how to be respectful, better friends, better futures. And at his age, that is less likely. So, there is no need for you to feel frustrated. If it were me, I don't really feel offensed, I'd instead worry about whether he's going to get himself in trouble for talking that way to other people. In the end, stuttering really isn't a big deal. I stutter every day in front of my friends, and I don't even bother to hide it. (Because as long as what I say makes sense, then the process of talking, even you look funny and stupid, doesn't matter, because the communication is meaningful.Talking is to communicate, not to make you look cool. (Of course, in front of strangers I will try to avoid embarrassment.)