I sincerely doubt they'd be asking that. Many of them would probably be happy we'd moved past that point.

https://www.history.com/news/declaration-of-independence-deleted-anti-slavery-clause-jefferson

My understanding is that many of them saw it as more of a necessary evil vaguely justified on racial grounds. We need to be willing to talk about and acknowledge America's racist history with the slave trade, but we also need to understand the era and the fact that it was never broadly accepted as the right way to do things.

This might make folks uncomfortable, but it's not all that dissimilar to folks buying cheap imported stuff today built primarily for the US consumer in sweatshop conditions, via outright slavery, and/or with various child labor schemes often at an extreme cost to the health of the environment. We've made things better but we've also recreated some of the problems that we'd destroyed in the WW II era with the justification of indirection ("well I didn't do it, the big company I bought from did it") instead of racism.

I fully expect a future generation to hold us to the pitchforks for buying cheap junk on Amazon or at Walmart and not ever asking "what behavior am I supporting? How did they make this at this price?"

That’s not the question they would ask. Slaves were considered property, not people. Well, until they became 3/5 of a person. And finally, much later on a full person.