The Ethical Slave is a fantasy, an idealistic impossibility constructed by over zealous individuals. I have heard the argument that the perfect solution to military and economic ills is to capture POW's as a slave labor force. This idea seems like a viable way to treat combatants until one examines the ineffable moral obstacles it presents.
Firstly, nobody can expect human beings like us to reaping generously to a subjugated populace. By simple human nature no man would treat equally the man he has been told that he is superior than. By placing others in a state of lesser status as a subhuman machine designed to carry out our tasks, a superiority complex is inevitable and the oppressor that is the slave owner can not help himself but to feel embiggened over his slaves. No man could resist the temptation to treat those that have been established as inferior like scum. And with that fell stroke all moral high ground has left the argument, but less us continue further.
There is also the problem of the nature of wars from which prisoners arise. If slaves from our wars were to become common nature, certain patterns would emerge. If the wars we fight are against Arab Muslims, then as happened in America before the types of people who are brought as slaves will be categorized with broad strokes as inferior, evil, and summarily deserving of slavery. All native Arabs will be suspected as escaped slaves and treated as second-class citizens until all who resemble the race of the combatant are slaves. The human nature to group and find patterns can not be stopped and will lead to a surge in racist castes if slavery of POWs were to be instituted.
Lastly, comes greed. Money as we all know sticks it grimy paws into every corner of civility corrupting it with inaction and oppression for personal gain. If slaves were to be profitable as presumably they would be why would anyone want to stop the supply of them? Why should we stop having a supply of slaves and money? War, a time-honored tradition of treachery, would become a commonplace business expenditure as people set nations ablaze for he sake of the almighty dollar. Man fighting man to help the fat cat catch his mouse. But then what if wars aren't enough? What if it seems to costly to fly soldiers across the world to collect tribute laborers? Surely there is a simpler solution nearby! Why not utilize the useless prisoner that so often gets treated as royalty? But then if we enslave the prisoner surely the debtor should be made into a slave being the burden on society that he is. Then why not take all burdens on society and enslave them? Social security recipients could all be slaves to make the selves useful. Of course the majority of Social Security recipients are retired and aging, but that is a detail to be worked out later.
There is no ethical slavery. There is the deluded vision of such a reality; however, it could never exist. In order to accomplish such an immoral task one must become a snake who slithers through the purposeful rocks of justice and equality to reach the barren wasteland of iniquity. No happiness comes from false superiority; no prosperity can be happily derived from the suffering of others.