This is utterly false. Did you think I didn’t know Exodus 21:21, the exception to verse 20? God says that if an owner hits his slave with a rod and the slave doesn’t die the same day then the oner is not punishment because the slave was his property. This means that hitting a slave with a rod, even one just paying back a debt.
It doesn’t say any permanent injury just the loss of a tooth or eye. There are a great many ways to harm someone that don’t involve hitting them in the head. In fact, let’s go back to the South Carolina Slave Code. It too punishes an owner for purposefully killing a slave or doing things like gouging out a slave’s eye, removing a limb, or castrating a slave. Again, there is no real difference between Biblical slavery and so-called chattel slavery.
But by what you quoted a Hebrew slave could be beaten with a rod so long as it didn’t knock out a tooth or eye or kill them that day. A slow painful lingering death was perfectly acceptable.
Beyond what I’ve already written he’s one final lesson I’ve written in other related threads:
We all know of politicians who at one time have said one thing and in practice done another. Imagine a made-up politician who talks about how much he loves the troops, but then slashes funding for veteran’s hospitals and armor for troops. He puts them into unnecessary conflicts and doesn’t give them the support needed to do extract themselves from combat safely. No person would look just at the words of that person and say the politician is for the troops. Two things are true: The specific is more telling than the vague. and actions speak louder than words. Any vague passages that say to be nice to slaves wither when compared to the many other passages that give very specific means to enact cruelty on others.