Okay, I'll try my hand at your questions, Nikki.
Is the Book of Mormon racist? Sort of. It was authored by Nephites, some of whom were censured because of racism:
Jacob 3:5 Behold, the Lamanites your brethren, whom ye hate because of their filthiness and the cursing which hath come upon their skins, are more righteous than you....
More commonly, accusations of racism are based on a superficial reading of the text--light skin good, dark skin bad--which fails to take into account several points to the contrary. First, it says they were marked on their skin
for unbelief, but these marks also included light-skinned unbelievers who painted their foreheads. It also goes on to list a dark-skinned
believer as one of the greatest prophets of the book who was yet rejected by most of the light-skinned people, and says that the (dark-skinned) People of Ammon had
greater faith than any of the light-skinned people. These are only three of the dozens of examples that fly in the face of such "dark skin bad, white skin good" overgeneralizations.
To look at one of these examples in-depth, let's examine the case of the Amlicites, who marked themselves to separate themselves from the Nephites. In Alma chapter 3, we are first given an explanation for the "mark" placed on the Lamanites:
7 And their brethren sought to destroy them, therefore they were cursed; and the Lord God set a mark upon them, yea, upon Laman and Lemuel, and also the sons of Ishmael, and Ishmaelitish women.
8 And this was done that their seed might be distinguished from the seed of their brethren, that thereby the Lord God might preserve his people, that they might not mix and believe in incorrect traditions which would prove their destruction.
9 And it came to pass that whosoever did mingle his seed with that of the Lamanites did bring the same curse upon his seed.
(Emphasis added)
Thus, the purpose was to mark them
as unbelievers, not to mark them as inferior beings. Compare this with the Biblical passage about being "unequally yoked with unbelievers" (2 Cor 6:14), yet another passage that has been quoted out of context to support racism.
The passage goes on to explain the mark placed on the Amlicites:
13 Now we will return again to the Amlicites, for they also had a mark set upon them; yea, they set the mark upon themselves, yea, even a mark of red upon their foreheads.
14 Thus the word of God is fulfilled, for these are the words which he said to Nephi: Behold, the Lamanites have I cursed, and I will set a mark on them that they and their seed may be separated from thee and thy seed, from this time henceforth and forever, except they repent of their wickedness and turn to me that I may have mercy upon them.
15 And again: I will set a mark upon him that mingleth his seed with thy brethren, that they may be cursed also.
16 And again: I will set a mark upon him that fighteth against thee and thy seed.
17 And again, I say he that departeth from thee shall no more be called thy seed; and I will bless thee, and whomsoever shall be called thy seed, henceforth and forever; and these were the promises of the Lord unto Nephi and to his seed.
18 Now the Amlicites knew not that they were fulfilling the words of God when they began to mark themselves in their foreheads; nevertheless they had come out in open rebellion against God; therefore it was expedient that the curse should fall upon them.
Now here we have the Lord getting credit for the mark placed on the Amlicites, which they actually placed on themselves. This is hardly the miraculous "marking" that is conveyed by the drastic oversimplifications--i.e. "make God mad, skin turns dark." It's quite likely that the darkening of the skin of the Lamanites was equally un-miraculous--the most likely cause was that many or most of Ishmael's family had Bedoin blood, as suggested by Hugh Nibley (Lehi in the Desert, 1952).
Thus, the entire purpose of the "curse" was not to denote inferiority but to warn Nephites from intermarriage with unbelievers. Is it easy to misinterpret this as racism? Absolutely, as evidenced by Jacob's words above and the other racist actions by Nephites. But when all the racial episodes in the Book of Mormon are added up, they are far in favor of racial equality. In that light, I think Elder Petersen readily accepted a superficial layman's interpretation without making a more thoughtful study.