Matt Asks:

Other than being post industrial, how different is say, the slave society of the antebellum South vs that of the Roman Empire?

Good question. The most obvious difference is that the antebellum South practiced racialized slavery, whereas the Roman Empire would enslave barbarians and Romans alike, and saw slavery as more of an economic status which one could enter or leave rather than a permanent identity. 

Next and relatedly, I would say that the two systems treated manumission and freedmen very differently. Clientalism – the practice whereby wealthy patrons provided goods, opportunity, and access to their clients in exchange for the votes and other services of their clients – was a foundational element of Roman politics and society. Upon gaining their freedom, manumitted slaves automatically became clients of their former masters, so elites saw manumission as a way to promote their political careers while still maintaining a good deal of influence. 

By contrast, manumission was pretty quickly seen as a threat to the operation of the Southern system. When the whole system is premised on the idea of white = free, black = slave, a population of free blacks not only posed a major ideological problem (it interferes with the whole mudsill theory, it raises difficult legal questions about the status and rights of freedmen, and it introduces the idea that slaves are actually people), but also potentially could be a fifth column within Southern society operating against slavery. It’s not an accident, therefore, that after each major rebellion in the South – Bacon’s Rebellion, Denmark Vesey’s Rebellion, Nat Turner’s Rebellion – that laws were passed restricting manumission and/or restricting the rights of freedmen.