You have got to let me borrow your Tardis sometime. No, he's not right, he's full of shit. Sure, we didn't firmly reject slavery until the transition from an agrarian to an industrial economy, but we rejected the cruelties of serfdom and slavery once we were able to do without them, and we have, painfully slowly, been simultaneously rejecting the cruelties of industry and figuring out how to do without them for 200 years, with some backsliding over the past few decades because 'Murica. How moral society can be is constrained by what it needs to do to keep functioning, Maslow's hierarchy at the collective level, but solving the practical problems that necessitate cruelty allows us to be less cruel, and when we are able to be less cruel we do. We as a collective learn to be better just as we as individuals do. Join the 19th century, put down the classical economists and pick up Hegel or Marx, depending on what you want to take as prior.