(like Joseph with Potiphar).
And Joseph refused to go along with the immoral advances of Potiphar's wife; so as a slave he needed to uphold godly principles, and not to do just whatever his owner or owner's wife wanted.
And Paul talks about the slavery of sin. If ones are so aghast to slavery, they might do well to deal with all which is so damaging, of slavery to sin. Ones can be so outspoken against slavery which is physical, right while they stay in slavery to unforgivenesss, worry, workaholism, arguing, and self-righteous judging which ruin people and their relationships, and keep them from being examples to their children so their children can grow up knowing how to love in a close relationship. And then the children can become slaves of various sorts of pleasure seeking, and drugs, and adrenaline rush seeking. And ones are tangled and mangled in their political struggling to legalize various degrading things, so they can have their treasured sexual pleasures without learning how to love.
And in the weakness for a treasure pleasure is also weakness to suffer emotional pain and fail to stay clear of arguing and complaining and blaming.
But this slavery has a way of not getting so much attention, while attention is decoyed to trying to control what people do outwardly. But there are people who understand how we need to get free of our slavery to sin, but also do what we can to stop the kidnapping and slavery of children and others.
I see that especially any illegal slavery needs to be stopped. The slavery in the time of Paul, which he was talking about, was legal though it probably could be abusive like American southern slavery could be. It seems some number of the southern American slave owners were in slavery to their own fear . . . fearing how at any time their slaves might rebel and slaughter the slave owners. And if they could sacrifice the lives of their sons in civil war, in order to have things their own way . . . possibly they were in deep slavery to how they wanted to live, versus valuing how Jesus has us loving.
So, it can be that in order to have slaves, the owner has to be a slave to what is much more deeply degrading than just outward slavery.