At one time the Church of Jesus Christ Latter-Day Saints argued polygamy as practiced by the FLDS cult was essential to salvation.
For example, citing the opinion of the United States Supreme Court in the case of Reynolds v. United States case (98 U.S. 145), George Reynolds, Brigham Young's personal secretary, plead as follows:
On the trial, the plaintiff in error, the accused, proved that at the time of his alleged second marriage he was, and for many years before had been, a member of the Church of Jesus Christ of Latter-Day Saints, commonly called the Mormon Church, and a believer in its doctrines; that it was an accepted doctrine of that church "that it was the duty of male members of said church, circumstances permitting, to practise polygamy; . . . that this duty was enjoined by different books which the members of said church believed to be to divine origin, and among others the Holy Bible, and also that the members of the church believed that the practice of polygamy was directly enjoined upon the male members thereof by the Almighty God, in a revelation to Joseph Smith, the founder and prophet of said church; that the failing or refusing to practise polygamy by such male members of said church, when circumstances would admit, would be punished, and that the penalty for such failure and refusal would be damnation in the life to come." He also proved "that he had received permission from the recognized authorities in said church to enter into polygamous marriage; . . . that Daniel H. Wells, one having authority in said church to perform the marriage ceremony, married the said defendant on or about the time the crime is alleged to have been committed, to some woman by the name of Schofield, and that such marriage ceremony was performed under and pursuant to the doctrines of said church."It should also be noted the LDS Church steadfastly resisted all attempts to abandon the Principal (of polygamy) until the church was disbanded as a criminal organization under the Edmunds-Tucker Act of 1887 and their property ordered seized.
Furthermore, many in the LDS Church ignored President Woodruff's instructions to abandon polygamy until the Church was embarrassed in the Smoot Hearings (1904-07), at which time two members of the Quorum of Twelve Apostles (among others) were expelled from the brotherhood by a Second Manifesto for increasing their number of polygamous wives.
Finally, it should be noted every LDS Church President openly practiced polygamy for over 120 years beginning with Joseph Smith in 1833 [when he "married" Fannie Alger after impregnating the 16-year old] and continuing through 1945 and Heber Grant (above).
In light of the above, I find attempts by current LDS members to distance themselves from their FLDS cousins on the grounds polygamy is morally and/or spiritually and/or doctrinally wrong both amusing and disingenuous.