Slavery was the one great stain on the founding generation, one which cost later generations rivers of blood and mountains of treasure to rectify.
But why was it a stain? Because, it violated the very principles they fought for.
However, their failure to carry their principles through to full fruition doesn’t change the righteousness of the principle.
And finally, why do you think you’re better than the founders? You just posted an absurdity that negated the principle that you are criticizing them for neglecting.
“And finally, why do you think you’re better than the founders?”
You’re deluded to come to that conclusion.