The plan of salvation called for a Savior to redeem fallen mankind from their condition of sinfulness on condition of faith in Christ, repentance, baptism, reception of the Holy Ghost, and continued obedience to gospel principles and ordinances. Redeeming one in sin would go counter to the plan of salvation and would destroy agency and accountability (see Alma 11:34, 37).
In the premortals councils of heaven, by stating that he would save them all Lucifer essentially proposed the redemption of all men and women in their sins. “If you undertake to save all,” said Brigham Young, “you must save them in unrighteousness and corruption” (JD 13:282).
Elder Orson Pratt also taught the difference between the Father’s plan to save his children from sin and Lucifer’s design to save all mankind in their sins.
“There must be an agency wherever intelligence exists, and without agency no intelligent beings could exist; and ... Satan sought to destroy this ... and to redeem them all in their sins”
(JD 21:288).
This distinction seems important in light of the philosophies of anti-Christs in the Book of Mormon (and in modern days) who claim “that all mankind should be saved at the last day, and that they need not fear nor tremble ... for the Lord ... had also redeemed all men; and, in the end, all men should have eternal life” (Alma 1:4; see also 2 Nephi 28:8).