(I missed this comment earlier)
The video is completely wrong about that too.
The history of race & faith in the USA is a complicated one. In the 1800's the US was still a slave nation, and many Christian congregations uses the Bible to justify that slavery. Even those which did not, congregations were strictly separated by race. Early LDS Christians bucked this trend: openly abolitionists and inviting black members to be part of their congregations, even being priests over white members. Such stances contributed to them being driven out of 3 different US states, to flee to what was then completely unoccupied and inhospitable territory (now known Utah).
Tensions were very tight between the US government and the LDS Christian Utah-ites, with the US government literally sending out the military to forcefully to occupy UT as one point. Somewhere in this early UT time period, a church policy came about to not ordain any more blacks to be priests, though congregations were still inter-racial (always have been). Why/when exactly this policy came to be, historians don't really know. The personal racism of Brigham Young was undoubtably a contributing factor (yes, all mortal leaders are mortal and have flaws, and policies are human things which change over time). This policy was later officially revoked via revelation from God.
A more in-depth write up of things:
Race and the Priesthood