If you actually dig up the truth about the civil war it gets even worse. If most soldiers on both sides knew what they were fighting for they would of gone home. The southern soldiers did not own slaves and the northern ones did not care.
Truth is overwhelmingly northerners did not care about black rights they thought they were defending themselves. There was no righteous outrage outside a small group of almost entirely women , it was a fight for survival as far as the northerners were concerned.
For the politicians it was a power grab or for a small few a fight to preserve the union , but had nothing to do with slavery.
In many respects civil war history is like holocaust history. A lot of rewriting to make the so called good guys look good. (Spoiler Alert) Every major government knew and many if not most people in the civilized world knew about what was happening they just did not care. The only surprise was how effective the nazis were at it. The outrage after WW2 was manufactured and sadly that is why antisemitism is still with us. The same applies to the civil war. If the northerners cared jim crow and the other horrors inflicted on blacks would not have been allowed to happen.