Northern states: "Treating workers like bought property is wrong!"
Treats workers like rented property instead

in all honesty, slavery only ended because the industrial revolution and factories made slave labor obsolete and unethical. Why force people against their will to work for you for free which potentially can end up with riots or slave uprisings?

You could just own machines that are hand operated, hire a bunch of people, and pay them dollars a day; they don't have to work for you either. This newer system benefited everybody. Even if you worked slave wages, at least you got compensated somehow.