Dude, I understand how historical context works. The point is, it doesn’t matter what point in time you are in, “slavery is wrong” is always correct. Just because it was happening everywhere, doesn’t mean that those people weren’t objectively immoral and incorrect for doing it. It doesn’t mean that people born into slavery suffered any less.
Not to mention that the southern slave owners in the US used the Bible to justify their chattel slavery. Making the fact that it’s in there even worse.
If someone has to think about the question, “is slavery bad” for more than a second or two, or if they begin their answer with something about historical context being important: that person is a piece of shit.