LDS belief states that every thing God creates for our salvation is for our benefit, even hell, which we believe is remedial in nature. Eventually hell and death will yield up its dead and every knee will bend and every tongue confess Christ. It's not that "only Mormons" will be saved, but the fact that all will be of one mind and one spirit, and there will be no name tags. All ordinances for the good of man, like baptism, must be administered by legal administrators of God's Kingdom, be they ancient or modern. As Joseph Smith said, a man cannot be saved or damned in ignorance.