I was wondering, since I've heard this a lot and I've done some research about it. I'd like to know what Mormons, at least contemporary Mormons, have to say about this.
Keeping in mind documents like these which I will quote to avoid needless opposition :
"Cain was cursed with dark skin; he became the father of the Negroes, and those spirits wh are not worthy to receive the priesthood are born through his lineage." (Mormon Doctrine, pp. 102)
"Negroes in this life are denied the priesthood; under no circumstances can they hold this delegation of authority from the Almighty" (Mormon Doctrine, 10th printing, pages 527-528)
"The gospel message of salvation is not carried affirmatively to them... Negros are not equal with other races where the receipt of certain spiritual blessings are concerned."(Bruce R. McConkie: Highlights From His Life & Teachings. Horn, Denis B.(2000))
I will now UPDATE the preface because the previous quotes were seemingly not enough to avoid needless opposition. I am not doing this to simply mock, I am doing this to get a satisfactory answer meaning truth.
Quotes from MORMON PROPHETS that are considered to be infallible teachings of the LDS, or supposedly so, we shall see.
Because of [Cain's] wickedness he became the father of an inferior race...the mark which was placed on Cain and which his posterity inherited was the black skin. (Prophet Joseph Fielding Smith, the way of perfection p. 101, 107)
Some classes of the human family...are black, uncouth, uncomely, disagreable and low in their habits, wild and seemingly deprived of nearly all the blessings of the intelligence that is generally bestowed upon mankinnd. The first man who committed the odious crime of killing one of his bretheren will be cursed... the Lord put a mark upon Cain which is the flat nose and black skin.
Shall I tell you the law of God in regards to the African race? If the white man who belongs to the chosen seed mixes his blood with the seed of Cain, the penalty under the law of God is death on the spot. **This shall always be so.
(2nd Prophet of the LDS Church, Brigham Young, "Journal of Discourses," Vol. 7, Pages 290 & 291)
The intermarriage of the Negro and white races, a concept which has heretofore been most repugnant to most normal minded people... There is a growing tendency...toward the breaking down of the race barriers in the matter of intermarriage between whites and blacks, but it does not have the sanction of the Church and is contrary to Church doctrine. (8th Prophet of the LDS Church, George Albert Smith, letter to Virgil H. Sponberg (critic of the anti-black ban), May 5, 1947, quoted in Lester E. Bush, Mormonism's Negro Doctrine: An Historical Overview, p. 42)
Here are some links :
Please, if somehow the LDS's official Church teaching has changed, explain in your answer the difference between the old theology and the new theology, that is a prerequisit to get your answer validated, thank you in advance.
considered to be infallibleNo LDS prophet is believed to be infallible (source).