We learn from the past, failures and successes, but we live in the present and plan for the future.
It's our nature to repeat our failures. Christianity is all about overcoming that nature. We can't overcome the nature of another person.
What in the history of blacks is preventing them from moving ahead in the future? If they are celebrating their achievements of fighting against racism, oppression, and discrimination, what are those achievements?
Of course you could say that securing the passage of the Civil Rights laws is an achievement, but what has been the result of that victory? That's also history that needs to be examined.