Ben, thank you so much for this thoughtful response. You are probably correct that the church would not declare Joseph was wrong on the polygamy revelation, and perhaps I should have relegated that to the unlikely section (or at least made the other option subordinate to it). Certainly, declaring monogamy the eternal and sole law of heavenly marriage could still accept Joseph’s revelation as inspired, as Eugene England so eloquently expresses.
However, I do believe that declaring Joseph to not be inspired on an individual point does not sink his prophethood. It cannot. It must not. President Uchtdorf said in 2013, “[T]o be perfectly frank, there have been times when members or leaders in the Church have simply made mistakes.” And maybe he was only referring to personal life — maybe that doesn’t include prophetic utterances. But I don’t think that’s true — I don’t think we have a doctrine of infallibility (though there is the Woodruff quote on never leading us astray). There’s a saying — “Catholics say the pope is infallible but don’t really believe it; Mormons say the prophet is fallible but don’t really believe it.” Could we believe it?
And on your other point, very fair that the church does not teach polygamy as a requirement for exaltation. But it doesn’t teach that it’s not one either. It just doesn’t teach anything on the subject. That’s something I’d love to see change, even if the conclusion is not one that I personally want. So you’re completely correct that the men who are creating rifts in their marriages through this doctrine are, essentially, exercising unrighteous dominion.