Great question. For decades in most of the South and much of the country, slavery was taught in a way to minimize the horrors of the practice while simultaneously reinforcing white supremacy.
This was all part of the propagation of the Lost Cause narrative, that was created expressly to teach that:
- Secession was lawful and justified: It asserted that the southern states had legitimately exercised their constitutional rights to secede from the Union over issues like state's rights and northern oppression.
- Slavery was not the main cause: It downplayed the role of slavery as the principal cause of the war, instead emphasizing issues like states' rights, northern aggression, and the preservation of the southern way of life.
- The Confederacy was morally superior: It portrayed the Confederacy as morally upright, and its leaders and soldiers as honorable, chivalric, and fighting for a just cause against northern aggression.
- The South was overwhelmed: It argued that the South was ultimately overwhelmed by the North's greater population, industrial capacity, and resources, rather than being defeated on the battlefield.
- Confederate soldiers were superior: It celebrated the Confederate soldiers' skill, valor, and commitment, often depicting them as underdogs fighting heroically against long odds.
The Lost Cause theory was propagated through writings, memoirs, speeches, and the establishment of memorial associations and monuments. It helped shape a positive historical memory of the Confederacy and provided a way for Southerners to cope with the trauma of defeat while setting aside the issue of slavery.
So, to answer your question, teaching about black slave owners might help soften the perception of the obvious role wealthy whites had in propagating and preserving slavery in our country. The problem is, that same message would be counter to the additional goal of reinforcing white supremacy while denigrating blacks as the inferior race incapable of autonomy and self-governance.