I'm 68--old, but not ancient. My daddy was born in 1910. That was 45 years after the end of the Civil War.
It occurred to me recently that this year marks the 45th anniversary of the end of the Vietnam War. Think about how tender feelings still are regarding it.
My point is that, given what the Civil War was, it should not be surprising that the cultural scars associated with it are not fully healed. In terms of generations, it was not all that long ago.
The racism that has marred the culture in which this nation formed, from 1619 to the present, is a blight on human history. We have made progress, but it will take yet more time to eradicate it completely.
One thing that would help would be an advance in out understanding of what justice is. For that, "Equality Is All We Need" (here in Medium).