No, it means that, as I said, the only reason that Antebellum white America was able to justify the inhuman cruelty they inflicted on black people is that they convinced themselves that black people weren't people.

That we were somehow fundamentally different to them, and therefore deserved the treatment we received.

They would never have tolerated seeing their own brothers and sisters, their own sons and daughters treated this way.

This lie is what made all the rest of it possible. And while (as you astutely point out), most people will verbally agree with this, there are all kinds of ways in which it doesn't quite match their true thoughts and actions.