Thanks for clarifying, I wonder, how should we best explain this part of the Bible when confronted by atheists or non-Christians who claim that the Bible ''supports'' slavery.
We should discuss it with great care and with people who are willing to explore the truth. If they're not willing, say your bit and leave.
Firstly, I would tell them that they can't judge/interpret a book that's a few thousand years old as if it were written today. Historical and cultural context must be adhered to. Remind them that the ancient world was a much more violent and chaotic place than we have today.
Given that introduction, I would then explore actual Bible verses in their context to show that 'slavery', as practised by the Jewish people, was very different to slavery as practised by their pagan neighbours.
Finally, I would finish up the bulk of the talk with a discussion about what indentured servitude really is and how it's very different to slavery as we know it eg. which was more in line with the pagan nation practices. Provide examples of indentured servitude. eg. economic models we have to this day in employees being indebted to their employers.
If that doesn't help to change a person's mind about what the Bible really says about 'slavery', I don't know what will. At the very least, they'll be well informed to make their own choice about what to believe. Holy Spirit will do the rest.