I would understand his remark if the princess was the daughter of a servant and the duke but dude she's a legitimate daughter of the duchess who is the legal wife and you call her lowly? She's so brilliant that no tutor could teach her and her swordsmanship was praise by her knights. Even if the prince is a neglected prince, he's still a prince do you think insulting him and a duke's daughter is a right thing to do during monarchy rule? This is just stupid plot at this point.