As Christians we are commanded by God to stand with the most vulnerable in our world, with those at the margins of our society. In the United States of America one of those groups is people of color in particular black people.
In order for slavery to work, in order for us to buy, sell, beat, and trade people like animals, Americans had to completely dehumanize slaves. And whether we directly participated in that or were simply a member of a culture that at one time normalized that behavior, it shaped us.
We can’t undo that level of dehumanizing in one or two generations. All lives matter, but not all lives need to be pulled back into moral inclusion. Not all people were subjected to the psychological process of demonizing and being made less than human so we could justify the inhumane practice of slavery.