I was reminded again recently of how much insane, socially unacceptable, and terribly, terribly cruel, stuff is in the Bible. The writings that were compiled into that text were products of their time... and it was a fairly brutal chapter in human history. Today most but, rather stunningly, not all Christians would not support the idea of killing rebellious children, as that most recent example makes clear. The rejection of violent, homicidal, and genocidal, Biblical passages only really presents a problem for fundamentalists who still insist that every word in the book is the true and irrefutable word of God. Having been raised Episcopalian, leave say, I learned to look at the Bible through a somewhat different lens.
As Brian Keith Dalton, aka. Mister Deity, points out, this is much trickier for Mormons. Dalton, who apparently was a Mormon, explains that the Book of Mormon is literally true and "the most correct book on Earth" under Mormon doctrine. That makes it much harder to gaffe off the wackiest bits.
The racism that was so acceptable in the time of Joseph Smith is forever enshrined as unassailable truth in Mormonism. That would seem to leave non-racist Mormons -- let alone black Mormons -- with little to fall back on other than cognitive dissonance.