I think that a religious debate was politically hijacked in 1890, and the Mormons, specifically their prophet, gave in. Was it disgusting? Probably, but if they can live with the change in their beliefs, good for them. I don't take that to mean that Muslims or adherents of other religions must do the same.
FWIW, I don't think that Mormons are liars, but as someone who is not Mormon, I do think they are wrong. I don't hold that against them any more than anyone else whose religion I don't buy into.
Personally, I don't have a problem with plural marriages among consenting adults, if that is a part of your religion. I have a problem when participants are underage, coerced, or unaware of the situation. Barring that, keep the government out of marriage.
That the Mormons are no longer polygamists is probably to their advantage, though.
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"Intellectual brilliance is no guarantee against being dead wrong." -Carl Sagan