She had A heart – how shall I say? – too soon made glad. Too easily impressed: she liked whate’er She looked on, and her looks went everywhere. (21-24)
When was the last time you heard someone complain because their spouse found joy and pleasure in too many things? "Man, I can’t stand my wife, she’s happy all the time," you might imagine the Duke saying. The Duke fantasizes that this pleasure in the world implies that his wife is promiscuous – a stretch, to say the least.
Oh sir, she smiled, no doubt, Whene’er I passed her; but who passed without Much the same smile? (43-5)
The Duke thinks of kindness as less valuable if it isn’t selective. As he portrays her, the Duchess is a kind and attentive wife to him, but that means less, in his mind, because she’s kind and attentive to everyone. He wants her to save all her affection for him alone – classic controlling abusive husband stuff.