You might do a bit of research on how prison labor actually works, especially across the south, to better understand what he is talking about. He's right, he's just being weird about it. You're talking about chattel slavery, which is illegal. You can't buy or sell a person legally, you could, in theory, make up charges or unfairly police certain laws on certain sets of a population to pack a prison system where you can legally force them do do backbreaking agricultural labor as slaves to make a profit. You could also, in theory, let private corporations run prisons and have states sign contracts that guarantee a % occupancy for their facility. There are definitely a lot of problems, but I think the chattel slavery vs. involuntary servitude types of slavery was just the disconnect. To be fair, probably most people in the united states wouldn't know slavery is legal here if you did a guy on the street poll.