I kinda see things from the duke's point of view - a noble marriage is a political arrangement, and his family is of higher rank. Who the hell does Ginger think she is, saying she'll end it because her betrothed is fooling around? Hell, if he'd counseled her by pointing out that affairs conducted out of the public eye are the norm and that she should probably not take the arrangement personally, I'd have respected him. But he did take the most obnoxious track, so feth it. Ginger's funnier with the king anyway.