DiogenesLamp referring to a PA slave case: "It says as of 1802, Flora was a slave.
One does not need to do a lot of contemplation to grasp the significance of this ruling.
Again, slavery continued *in* Pennsylvania till at least 1840."
Of course, before the 13th Amendment, slavery was considered a matter for state laws to establish or abolish.
Most Northern states, like Pennsylvania, abolished their slavery gradually, over decades such that, for example, even in 1860 New Jersey recorded a handful of still slaves amongst their 25,000 freed blacks.
For comparison, a state like South Carolina had 400,000 slaves and about 10,000 freed blacks.
Your attempt to make a point reminds me of that old joke about a woman who would sleep with a man for a million bucks, but wouldn't do it for a couple of hundred. The punchline goes:
"We've already determined what sort of girl you are, now we are just haggling over the price."
If your position is that slavery is immoral, you shouldn't tolerate it at all. New Jersey tolerating any is a violation of their alleged principle. South Carolina having 400,000 is not a violation of theirs, because they didn't regard it as immoral.
But what of the territories? As a Federal matter, slavery was recognized as legal, and slaves were recognized as the legal property of their owners.
By what legitimate Federal authority could they assert that the territories must be "free?" By what application of constitutional law could they deprive a man of what the Constitution recognized as a right?
The territories had no state government to gain say them, even if you argue (as do you) that states could abolish this particular "property" right. How can a Federally governed territory speak to this issue at all?