They 100% would be making that argument during the time period(ignoring for a minute that the US still has slavery anyway). Heck, they still do, I grew up going to a school where our teachers seriously argued that the slaves were better off as slaves, with a much higher quality of life.
A few highlights I remember were them saying "slaves were usually never beaten because that would affect their ability to work" and "it gave structure to their life". Also "most slave owners were good people who were friends with their slaves".
Yeah Indiana gives the same education: "Look at this kind slave master! He is letting his slaves have a BBQ!" type of shit. Also remember doing assignments with prompts like "What are the pros and cons of slavery?" as if slavery has pros. As an adult... I wish I weren't such a "good kid".
Indiana also praises indebtured servitude. "Isn't this system great! Makes so much sense, if you owe someone money, you should be their slave for 7 years to pay it off instead of going to prison when you can't pay it back normally."