Are we meant to sympathise with the speaker of Robert Browning's 'My Last Duchess'?

The critic Robert Langbaum said that essence of dramatic monologues - poems like 'My Last Duchess,' where an invented character speaks the words, rather than an author or author-figure - was the 'tension between sympathy and moral judgment.' Why do you think this might be? Let's have a closer look at the poem and see if we agree. One thing that Browning does very skilfully in 'My Last Duchess' is present us with lots of different viewpoints, lots of perspectives from which the Duke Ferrara can be viewed. It's almost like a hall of mirrors, or a portrait gallery similar to the one the Duke is showing us. There's the Duke's perspective, the one most being spoken to us directly by the character. There's the perspective of the Duchess while she was alive: how might she have responded to the Duke's charge of infidelity? There's the perspective of Fra Pandolf, the painter who made the portrait, whom it seems the Duke envied for the access he had to the Duchess's mind and body: perhaps he would have sided with her. There's the perspective of the author, Robert Browning, which is never explicitly voiced, but which we might be able to pick up hints of - a good exercise we could do now would be to find some of those hints in the poem. And there's the perspective of the visitor who is receiving the tour, who appears to be trying to arrange a new marriage on the Duke's behalf. What might he feel? In many ways, he is similar to us, the readers of the poem. We are both are being given the grand tour, and both of us are forced to remain silent throughout, keeping any negative judgments we may have under wraps. If the visitor speaks up, he might scupper his chances of finding a match for his mistress. Is there a sense in which we, as readers, are silenced even after the poem ends? We cannot make our minds up on how to judge the speaker; we have too many perspectives to consider; the perspectives we have are too unreliable, too influenced by greed and jealousy and self-promotion. Maybe the tension of the dramatic monologue is that although it seems to present us with a flesh-and-blood human being, this person is only an illusion, a work of art. To really be sure of whether the Duke deserves our sympathy, we would like to grab him by the scruff of the neck and ask him some serious questions. Perhaps we could try this, as a dramatic exercise. What questions does the poem not answer about the Duke? What questions would you ask him if he were here with us? How would he respond?