Lauren
I went to your link, but I got paywalled out. But it's not hard to imagine how some Republicans will spin the 'three-fifths" into a moral strand. Actually the USA should bring it back, but this time it applies to white people!
There is a book called "Lies My Teacher Told Me". It repudiates much of the sanitized myth around the constitution, which is often taught at the high school level.
Unfortunately, there is a great political force to perpetuate the myth. Like many other places in the world, the USA does not want to be honest with its own history.