Some of our founders were faced with a bad choice. 1776 presents it well, Adams, Franklin, and Jefferson had to strike a passage opposing slavery they wanted to keep in order for the Declaration to pass.
I don't think we can blame them for yielding, it was a difficult choice. But we can question the men in Philadelphia both times who said they valued slavery MORE than they valued the new nation. In 1776 they were willing to remain under the crown than risk losing slavery. There is nothing wrong in pointing that out. We often accept some people were on the wrong side of history, ask the Pharisees how modern Christianity views them today.
When we cast our heroes into marble, they lose their humanity. Our founders, and I'll add Lincoln here too, were human with human frailties that marble does not, can not show. But it is their humanity we need to learn, they weren't demigods striding across America as a colossus. They were human, they had hopes and fears, they tried to do right but sometimes were not up to the task, and sometimes they committed sin. The more we encase all that in marble, the worse our modern leaders look. It isn't fair comparing any living, breathing, human to marbled perfection. The truth of the matter is they are better as humans than marble. Lincoln had to deal with the death of a son and the collapse of his wife while leading that terrible war. Lincoln certainly never believed in equality between the races, but still engaged in that war. His humanity makes him a more interesting character than the marble Lincoln ever would.