“Some Southerners insisted slavery must be acknowledged in the Constitution, as their price for ratification, and so it was done.”
I concede your point: at the time the Constitution was adopted, only 13 of the original 13 states were slave states. And of the 13 slave states, only nine were in the north. And of the nine northern slave states, only nine voted to include slavery in the Constitution.
Naw, you conceded nothing...
Jeffersondem: "at the time the Constitution was adopted, only 13 of the original 13 states were slave states."
More importantly, seven of nine Northern States had already begun gradual abolition, along with five future States of the Northwest Territories where slavery was outlawed by Congress.
Jeffersondem: "of the nine northern slave states, only nine voted to include slavery in the Constitution."
Only the Southern states insisted on recognizing slavery and even counting their "property" as 3/5 for representation purposes.
Of course in 1787 not all Southerners supported slavery and not all Northerners opposed.
By 1860, views had considerably hardened.
It is a common and calculated tactic of your ilk to conflate the original British Colonies with the original States of the United States. Slavery was foisted upon the Colonies by the British. The death knell for slavery in those Colonies began precisely with the creation of the US Constitution. The northern States began immediate steps for the eventual abolition of slavery concurrent with the creation of the Constitution. But I think you know that. The eventual ending of any importation of slaves was written into the Constitution.
Please try to be more specific with your broad brush generalizations. For example: "nine of the nine northern slave states voted to include slavery in the Constitution". Now do you understand how silly that sounds? Can you try to be more specific when you say "include slavery". Some people may get the wrong idea when people such as you and your ilk go running around spouting these tired lost cause memes.