"I'd be inclined to question whether having limited knowledge of a wider world than your own neighbourhood would really have been a significant factor in making people capable of the kind of detachment from human values that chattel slavery as developed in the USA required. It could well work completely the other way about.

"The people who drew up the American Constitution, and ensured that it left slavery alone, seem to have been quite a sophisticated and kwowledgeable bunch. That kind of sophistication can be quite handy in enabling people to have that sort of detachment."

But there's no denying that they were largely British in their outlook and education or that at the time the US Constitution was being drawn up, slavery was still legal in other British colonies. It wasn't fully banned by the British until much later (and bless the British, their solution to the problem was so much better than a Civil War). Not condemning, just pointing out that the framers of the Constitution weren't the only sophisticated people detached enough to let slavery continue.

What's more appalling is that slavery still exists in the US and other parts of the world. Oh, it's clandestine now, but I've read estimates as high as 50,000 for women held as slaves for the sex trade in the US alone. Some 150 women from South America were "freed" a couple of years ago not more than 25 miles from where I'm sitting. Migrant workers are often treated no better. Apparently you don't even have to have lived 230 years ago to find enslaving people economically attractive. Even some modern sensibilities are detached enough.

I can't think of a single excuse for condoning slavery at any point in history. No one accused of practicing it today would want me on their jury.