The Americans are not (to my knowledge) pointing a gun at Bangladeshi sweatshop owners and telling them “You must produce a quota by whatever means necessary.” The Americans might be benefitting from this arrangement, but if they refused to buy these products, it’s not like slave labor would disappear; it would just be redeployed into other sectors. The countries where this slavery occurs have to bear some level of responsibility for the things they permit to happen within their own borders, otherwise they were never sovereign countries to begin with, and they ought to be colonized by those powerful enough to enforce the rule of law.

Who do you argue is colonizing India at the moment?

Natural and unavoidable mean the same thing in the context the GP used them.

>Imprisonment was not a sentence under Roman statutory law,[2] though detention is mentioned in the Twelve Tables and throughout the Digest.[3] "Detention", however, includes debt bondage in the early Republic;[4] the wearing of chains (vincula publica), mainly for slaves; and during the Imperial era a sentence of hard labor at the mills, mines or quarries.[5] Slaves or lower-status citizens sentenced to hard labor were held in prison camps.[6]

>Incarceration (publica custodia) in facilities such as the Tullianum was intended to be a temporary measure prior to trial or execution; abuses of this principle occurred but were officially censured.[7] Located near the law courts, the Tullianum was used as a jail or holding cell for short periods before executions and as a site for executions.

So yes, as I said, imprisonment is a newer development. Holding people temporarily is jailing. Imprisonment, in the "sentenced to prison for a period of time or indefinitely" is a modern idea. It was considered barbaric by some cultures historically, but it also was just not viable. There was a small surplus of food, which was for the aristocracy to siphon off the top (ostensibly to fund the defence of the realm), not for feeding common criminals.

Stop trying to make incarceration seem like a long-running historical phenomenon. It is profit-driven propaganda, the promulgation of which began promptly in 1865.

Incarceration, in the Western legal tradition, is very new in relative terms, and its growth has been overwhelmingly the result of the experience of the USA transforming slavery into something marginally more politically acceptable.

You probably already know this, given your knowledge of the history, but some plantations, such as Angola, never even bothered closing down; they just transformed into penitentiaries and continued business as usual. The 13th amendment to the constitution, against the better judgment of many objectors, is specifically worded to facilitate this transformation.

Incarceration is not a legal tradition. It is a way to shoehorn slavery economics into one.

This is true of some forms of chattel slavery, but not of slavery in general. Most forms of slavery throughout history allow slaves some degree of personal property. This was often legally considered to be the property of the slave’s owner, but it was effectively controlled by the slave himself.

There isn’t anything inherent to industrialization which favors the use of free labor. One common argument is that mechanization required the use of more highly skilled laborers, which afforded greater leverage to laborers. This argument falls flat because we can see examples of even relatively sophisticated labor being performed by slaves. Consider the articles posted here recently about slavery in call centers in Myanmar and Thailand, where kidnapped victims are forced to perform scams. There are also the more widely known examples of sweatshops in Bangladesh.

Another argument that is often made is that factories have high amortization costs that require the factory to produce (and more importantly, sell) a high enough number of units in order to cover these costs. What I have not seen here is a compelling case as to why the propertied class of a slave-holding society would care about building factories for consumer goods if the unit economics were not already favorable.

You can go back and read the newspaper articles, speeches in parliament, pamphlets, etc. The historical record is unambiguous. Slavery was abhorrent. That was it.