Rape of slave women was a problem of the South, not in Utah which had a near zero population of slaveholders. It is asinine to suggest that Brigham was talking to Southern slaveholders from his pulpit in SLC in the 1850s. Ask him to show where in the context of that actual talk the intended audience is other than Mormons in the SL valley. It's just not there.
Also, Elder Mark Peterson, Race Problems as They Affect the Church, August 1954. A culture antipathetic towards "amalgamation" of the races, to use the pre-Civil war term, was propagated by Brigham and carried by the church into the 20th century, complete with Priesthood/temple ban. Decades of Mormon so-called prophets, seers, and revelators confused their own bigotry as being Gods will. No reason to listen to a thing that comes from their lips.
From the addendum to same:
[Quoting from, "The Way to Perfection" by President Joseph Fielding Smith]: "Our place among the tribes and nations evidently was assigned to us by the Lord. That there was an assignment of this kind before earth life began is a declaration of the scriptures. Certain spirits were chosen to come through the lineage of Abraham, and this choice was made in the beginning. Other selections were also made and the nations determined upon by the councils in the heavens. When Paul was speaking on Mars Hill, he said to the Athenians, "Ye men of Athens, I perceive that in all things ye are too superstitious, for as I passed by and beheld your devotions, I found an altar with this inscription, 'To the unknown God.' Whom therefore ye ignorantly worship, him declare I unto you. God that made the world and all things therein, seeing that He is Lord of heaven and earth dwelleth not in temples made with hands, neither is worshiped with men's hands as though he needed anything. Seeing He giveth to all life and breath and all things; and hath made of one blood all nations of men, for to dwell on the face of the earth, and hath determined the times before appointed and the bounds of their habitation."
From the addendum to same:
Why? If I were to marry a Negro woman and have children by her, my children would all be cursed as to the priesthood. Do I want my children cursed as to the priesthood? If there is one drop of Negro blood in my children, as I have read to you, they receive the curse. There isn't any argument, therefore, as to inter-marriage with the Negro, is there? There are 50 million Negroes in the United States. If they were to achieve complete absorption with the white race, think what that would do. With 50 million negroes inter-married with us, where would the priesthood be? who could hold it, in all America? Think what that would do to the work of the Church!
Now we are generous with the negro. We are willing that the Negro have the highest kind of education. I would be willing to let every Negro drive a Cadillac if they could afford it. I would be willing that they have all the advantages they can get out of life in the world, but let them enjoy these things among themselves. I think the Lord segregated the Negro and who is man to change that segregation? It reminds me of the scripture on marriage, "what God hath joined together, let not man put asunder." Only here we have the reverse of the thing--what God hath separated, let not man bring together again.