I’m not surprised about your experience though. I have also lived in the south and many of the southern states are still feeling the effects of decades of extensive lobbying on education by the Daughters of the Confederacy.
They DoC has historically pushed a narrative about slaves being happy and content overall, cared for by empathetic masters who valued their well-being. There are many monuments still standing glorifying the wartime deeds done by “loyal” and happy slaves. It’s really insidious.