The Mormons teach that we are not held responsible for the sins of Adam and Eve (in the Catholic Church a child is born with “Original Sin”–the sin of Adam and Eve). So….why would the Mormon Church teach that all generations of blacks are held responsible for the sin of Cain?
The concept of the “Original Sin” and the consequences of sins committed by our Father’s children in mortality are completely unrelated concepts. In the Catholic church infants are baptized to remove the consequences of the original sin. Although this is not a common practice in the Catholic Church, I have attended one baptism in which the sinful infant was not allowed to enter the church building until the evil spirits were exorcised from the infant–a rite that was performed by the priest on the porch of the church prior to bringing the infant into the building for the baptismal rite.
The Mormon Church teaches that We believe that men will be punished for their own sins, and not for Adam’s transgression (Second Article of Faith). Thus a new-born infant is considered to be pure, clean and free from all sin. As the child grows it becomes by degrees more and more responsible for its own behavior. Thus, the Lord has defined a minimum age of eight years for, if you will, the legal accountability before God for the consequences of the child’s own actions—
And again, inasmuch as parents have children in Zion, or in any of her stakes which are organized, that teach them not to understand the doctrine of repentance, faith in Christ the Son of the living God, and of baptism and the gift of the Holy Ghost by the laying on of the hands, when eight years old, the sin be upon the heads of the parents.
For this shall be a law unto the inhabitants of Zion, or in any of her stakes which are organized.
And their children shall be baptized for the remission of their sins when eight years old, and receive the laying on of the hands. (D&C 68:25-27)
Now, your statement that the Mormon Church teaches that all generations of blacks are held responsible for the sin of Cain, is not in any way correct. The blacks, as all other people, are held responsible only for their own sins. However, the consequences of the sins of one person may effect the lives of many others and most often usually does. Witness the following scriptures—
Thou shalt not make unto thee any graven image, or any likeness of any thing that is in heaven above, or that is in the earth beneath, or that is in the water under the earth:
Thou shalt not bow down thyself to them, nor serve them: for I the LORD thy God am a jealous God, visiting the iniquity of the fathers upon the children unto the third and fourth generation of them that hate me. (Exodus 20:4-5)
And again, verily I say unto you, if after thine enemy has come upon thee the first time, he repent and come unto thee praying thy forgiveness, thou shalt forgive him, and shalt hold it no more as a testimony against thine enemy–
And so on unto the second and third time; and as oft as thine enemy repenteth of the trespass wherewith he has trespassed against thee, thou shalt forgive him, until seventy times seven.
And if he trespass against thee and repent not the first time, nevertheless thou shalt forgive him.
And if he trespass against thee the second time, and repent not, nevertheless thou shalt forgive him.
And if he trespass against thee the third time, and repent not, thou shalt also forgive him.
But if he trespass against thee the fourth time thou shalt not forgive him, but shalt bring these testimonies before the Lord; and they shall not be blotted out until he repent and reward thee four-fold in all things wherewith he has trespassed against thee.
And if he do this, thou shalt forgive him with all thine heart; and if he do not this, I, the Lord, will avenge thee of thine enemy an hundred-fold;
And upon his children, and upon his children’s children of all them that hate me, unto the third and fourth generation (D&C 98:39-46).
Further, the implication of your statement is that the black skin given to the descendants of Cain was some sort of curse given to them. Actually nowhere does it say in the scriptures regarding Cain that the curse was black skin. It states that a mark was placed upon him. We don’t know what that mark was. But Cain does lament:
And Cain said unto the LORD, My punishment is greater than I can bear,
Behold, thou hast driven me out this day from the face of the earth; and from thy face shall I be hid; and I shall be a fugitive and a vagabond in the earth; and it shall come to pass, that every one that findeth me shall slay me (Genesis 4:13-14)
The Lord answered with these words:
And the LORD said unto him, Therefore whosoever slayeth Cain, vengeance shall be taken on him sevenfold. And the LORD set a mark upon Cain, lest any finding him should kill him (Genesis 4:15).
So a “mark” was put upon Cain to protect him from the ire of others. Cain was indeed cursed for his despicable action, but the curse was that neither he nor his descendants would have the right to hold the holy priesthood, as we learn from the Book of Abraham in the Pearl of Great Price—.
Now the first government of Egypt was established by Pharaoh, the eldest son of Egyptus, the daughter of Ham, and it was after the manner of the government of Ham, which was patriarchal.
Pharaoh, being a righteous man, established his kingdom and judged his people wisely and justly all his days, seeking earnestly to imitate that order established by the fathers in the first generations, in the days of the first patriarchal reign, even in the reign of Adam, and also of Noah, his father, who blessed him with the blessings of the earth, and with the blessings of wisdom, but cursed him as pertaining to the Priesthood (Abraham 1:25-26).
That priesthood curse was lifted from the descendants of Cain by the Prophet, Spencer W. Kimball, who received a revelation from God in June 1978 extending priesthood and temple blessings to all worthy male members of the Church (Doctrine & Covenants Official Declaration–2).