It is reductive to see this dramatic monologue as “Mysoginist” merely. True, the Duke seems to treat his spouses as objects, but the central point is that he treats everything as a possession—including his artwork (the statue of Neptune, the portrait of his last duchess, the mule, the gardener, the potential dowry that will accompany his next duchess, etc. This “possessive” attitude is part of a larger personality disorder—what, post-Freud, might be called a narcissistic, egocentric attitude toward all of life. Browning is drawing a portrait of a kind of person, with a title, to be sure, but emblematic as well of contemporaries (last half of 19th c.). We as readers must remember that when a poem is set in a past society, it nevertheless is addressing a subject on the poet’s mind as he or she writes the poem. If Browning were addressing only the male flaw of treating all women as inferiors, he would not have bothered with details of the duke’s disdain for art, etc. The point is that when all of Browning's work is examined, misogyny does not stand out as a major concern.