I think the best parallel to the issue of polygamy (at least from the point of view of moral culpability) is those rare cases of accidental bigamy that arise when a spouse is prematurely declared dead and the widow/widower remarries, only for the original spouse to turn up again years later (having spent the interim as a castaway, galley slave, prisoner of war, lunatic, etc). From the point of view of both the government and the surrounding society, the second marriage was perfectly legitimate, and did not violate the rights of the original spouse. So, how do you resolve the issue without suggesting that two wrongs make a right—that is, without appearing to break up a marriage contracted in good faith in the name of preserving the sanctity of another marriage contracted in the same way? It's telling that even Jesus dodges this one (or something close to it) in Mark 12, effectively saying, "Well, marriage serves a contigent purpose that will be fulfilled in the eschaton, so why are you assuming that there will be a neat answer to every question about who is really married to who, and which marriage takes precedence?" It's also significant that the early church appears to have granted that polygamy, while not ideal, would at least be tolerated among the laity, even if the clergy would be held to a higher standard (1 Timothy 3:2).
I think the best parallel to the issue of polygamy (at least from the point of view of moral culpability) is those rare cases of accidental bigamy that arise when a spouse is prematurely declared dead and the widow/widower remarries, only for the original spouse to turn up again years later (having spent the interim as a castaway, galley slave, prisoner of war, lunatic, etc). From the point of view of both the government and the surrounding society, the second marriage was perfectly legitimate, and did not violate the rights of the original spouse. So, how do you resolve the issue without suggesting that two wrongs make a right—that is, without appearing to break up a marriage contracted in good faith in the name of preserving the sanctity of another marriage contracted in the same way? It's telling that even Jesus dodges this one (or something close to it) in Mark 12, effectively saying, "Well, marriage serves a contigent purpose that will be fulfilled in the eschaton, so why are you assuming that there will be a neat answer to every question about who is really married to who, and which marriage takes precedence?" It's also significant that the early church appears to have granted that polygamy, while not ideal, would at least be tolerated among the laity, even if the clergy would be held to a higher standard (1 Timothy 3:2).