I highly recommend Margaret Blair Young's 3 part series at By Common Consent:
"All God's Critters: Some Thoughts on the Priesthood Restriction and Differing Opinions"
In part two she writes:
"But why should the origin of the ban matter at all, given that the LDS Church was part of a racist nation and that most religions in the 19th Century had some racialist policies? Isn’t all that history merely a sad footnote in the LDS story which was resolved in 1978?
I would say that it is a mere footnote. The central tenet of our faith is the atonement, and nothing else compares in significance. But that footnote does matter because it still affects us, our missionary efforts, and the retention of converts. The folklore which undergirded the philosophy has lingered. As recently as 2009, an African missionary in the Congo had his Anglo companion ask Elder Holland, who was dedicating the country of Cameroon, if it was true that blacks had been “less valiant” than others in the pre-existence. Elder Holland denounced the idea with characteristic boldness, and said that everyone on Earth was valiant in the pre-mortal world—or they wouldn’t be here. Other families of African lineage, or parents of adopted black children, have also felt the sting of the folklore, and continue to deal with a view which casts them as cursed. There are still Mormons who believe such things, which leads them to unthinkingly denigrate people of color (many colors), and to behave in a way which President Hinckley called antithetical to being “a true disciple of Christ” (April Conference 2006). That’s why it matters."Part one is here
Part two is here
Part three is here