I think that misstates the issue in 1787.
By 1787 only two Northern states had totally abolished slavery, and five more began very gradual abolition processes.
But in New York and New Jersey, slavery was still totally legal.
Point is: even by 1787 there was not yet universal agreement in the North that slavery should be abolished, and so there was no great confrontation at the Constitution Convention over that particular question.
Yes, around the margins there was much debate, especially over questions of how, logically, "property" could be counted as "people", and ending with the notorious 3/5 rule.
Today that 3/5 rule sounds, well, absurd, but practically speaking it gave Southern states something they desperately needed: substantially more representation than their voting white populations otherwise justified.
Hence the term: "the Slave Power".
Indeed, since Thomas Jefferson was the first President elected by "the Slave Power", he was given the moniker: the Black President.
They were still wrong, and frankly, they knew it.
Now Brother Joe, I don't want to upset you, but check my history.
If I recall, the South wanted “all other persons” to be counted as whole people for the purpose of political representation in Washington, but the northern states didn't want to count these human beings at all; or as one-half a human. These northern states were so, so ... well notorious, to use your word.
But I guess the 3/5 compromise was pretty cozy for the northern states (and the southern states too).
I can't understand how the northern states could do this (shaking my head). We need to take down the state flags of the notorious northern states. Every time I see the flags of one of the northern states I'm reminded of the 3/5th compromise and slavery.