A very long time ago slavery was a universal practice throughout the world with the possible exception of ancient India. All ancient societies participated slavery. In China during several dynasties a captured man would be castrated and forced into slave labor, his property would be seized and his family would be sold into slavery also.
During biblical times prisoners of war were pressed into slavery, foreign slaves became perpetual slaves of the slave owners. There was also debt slavery which sometimes was the only way people could feed themselves, and there was conjugal slavery where a girl would be sold under the understanding that she would marry the purchaser or his son, and failing that she would be redeemed.
The bible, being written during this era in human servitude, naturally addresses this in numerous areas. Detractors and people who hate a God they don't believe exists ignore the world wide practice and focus on those mentions in the bible as a misbegotten statement of blanket endorsement of slavery. While venting their spleens at Christians, these people seem to believe is that slavery ended with the Emancipation Proclamation, they are blissful in their ignorance that right now there are tens of millions of people trapped in various forms of slavery throughout the world today. Researchers estimate that 21 million are enslaved worldwide, generating $150 billion each year in illicit profits for traffickers. About 78% toil in forced labor slavery, about 22% are trapped in forced prostitution sex slavery, and the remaining 26% are children.
So while slavery is very real, and very horrible, our detractors fume about the one book in antiquity that actually addressed slavery for the sin that it was