One of the reasons why Northern Abolitionists thought slavery was horrible under the Democrat plantation is because it made the South poorer and disenfranchised white workers as well.
The South lacked any real industrial power because slave labor was undercutting white workers, while aggregating wealth under white land owners. In the North, people had to be paid, so it made more sense to make factories and other jobs that were highly productive on a per manpower basis. In a feudal system, the Industrial Revolution would never happen, because serfs wouldn’t be allowed the freedom to just move anywhere and work in any city, for any wage.
Slave was becoming dangerous not merely to the blacks, white people may not necessarily care about black strangers and their families, but because it was going to start affecting white workers, normal American families that had “equal” rights.
Some people even recognized that ahead of time, such as General Lee, but they weren’t given any power to reform the system. The system didn’t want to be changed and all the land owners in power, had the power to punish and destroy anybody that thought different. A few KKK episodes, a little bit of canning here and there, and nobody would be left to contest the issue. Even poor whites and normal middle American families had to obey Jim Crow or else be punished. The State’s Rights to tyrannize their own people, even without the Black Question being involved.
The author perceives power dynamics as being above and directly connected to economic dynamics. Most people don’t really think of it like that. They think technology will end slavery sooner or later, that it is inevitable. That economics will naturally balance out the power scale. They think if some top law makes the wages better or introduces a better way of doing things, that this naturally makes things more productive or more fair for everyone involved.
From what I’ve seen of human nature, that’s a little bit too idealistic.