People who get pissed at the duke... Your feeling js justified, but remember he WAS ALSO abused.
It is a given that not all of you protester understand how abused people think. He think he was beaten as a child because he did something wrong. Because he did not know his own value, the only one who dictate his value as a child is his abussive sister. But the duke know his son's value, and how kind and hardworking his son is, and there he found no justified reason to beat his son unlike when it was with him when he was a child. Just like how Abel think he deserves to be beaten, the Duke thought so too about himself.
I do not find anything weird with this. And his narccissitic tendency? Yeah he is probably insecure af.