The two things are quite different. The Lord God made all the people of all races. Race in and of itself is actually a picture of the creativity of God. Racism is used by Satan to divide, particularly in the U.S., and sadly, even in Christendom. It is a subtle appeal to the flesh to think that one's skin color or culture impute inherent worth or dishonor to oneself or others, and quite unbecoming of anyone indwelt by the Holy Spirit of God.
On the other hand, the Lord never told anyone to believe the lies of men like Joseph Smith and Brigham Young. In fact, he commanded us to rebuke them sharply, to oppose their lies with the truth, and to not receive them into our homes or even to wish them God speed (2 John 10, 11). Such is the way of the Deceiver that he will try to convince believers that they are wrong for obeying God and avoiding false teachers.
This does not mean, of course, that Christians should persecute poor, deluded Mormons (or Muslims or Hindus or any other pagan). Rather, we are to give them the gospel truth. Those who are persecuting Mormons are even more defiled than they, having been given up to uncleanness and a reprobate mind by God to do those things that are not convenient. May the Lord use their suffering to bring them to repentance!