Cloning technology is unlikely to result in the births of many cloned persons; no society so utterly consumed with its own wants is likely to be interested primarily in sharing the world with any new life. So even if we can set aside most of the Brave New World images of stultified servant classes, raised as property (though no doubt there will be an distasteful but lucrative trade in made-to order sex slaves, sterilised for both convenience's sake and to prevent accidental inbreeding) there remains the fact that the pulsing contents of many a test tube and petri dish will be held as property of the powerful.
We are an individual human being in the body first at conception and remain an individual human being in the body until death, artificially or naturally arrived at, along the continuum that is an individual human lifetime in the body begun at conception.
Slavery is unacceptable in an advanced civilization ... or is it? If it's enslavement for only a short time period, then harvest and kill the enslaved, is that okay?... They're only a few hundred cells.