[Bob]

To be clear, Madison is here talking about the importation of slaves from Africa, not their continued enslavement here or the selling of slaves inside the USA.

While that's true, it's often the case that one can't reach a desired goal in one leap. I think that preventing the importation of new slaves was a small, but necessary, step toward eliminating slavery in the US as a whole.

[TheBigIf]

And as one of his first acts as President, Thomas Jefferson passed the Abolition of Slavery Act outlawing the importation of any future slaves. Yes it was not a complete ban of slavery but was an important step in that direction in the fight against slavery.