If you found this series hard to watch, disgusting, or cruel; than congratulations, because that's the point.
It's depicting the horrific actions taken against African Americans. All of these events, all of the cruelties, they're taken from reality. These are things that actually happened.
If anything, the added touch of demonic ghosts was to make it manageable to view. It was to allow viewers a brief break from the truly agonizing scenes.
We like to turn away from history. Pretend we understand, then ignore it and move on. But a lot of people truly don't recongize how horrific this time period was.
This series did a great job at forcing people to look.