The "institution" did not make them keep their own slaves. The point which you are continuously trying to skirt is that the principles asserted for them and their real world actions went in different directions.
The notion that the Founders did not think the principles of the DOI applied to Africans is the rationale behind the Dred Scott decision. It was conclusively refuted in the dissents to that atrocity, and many, many times since.
Dred Scott would not have been possible but for the obvious examples of the founders who created the Declaration continuing to keep slaves. It is irrational to believe that they would see the principles in the Declaration as encompassing slaves while they continued to keep them.
If they believed that the declaration applied to slaves, they would have immediately released all of theirs.
A classic example of projection. Secession and war by the South being about much of anything other than slavery was indeed an after-the-fact rationale to justify a war fought for an immoral cause.
For the sake of argument, let us assert that the south had the worst possible motives for wanting their independence. These motives have nothing to do with the North's motives for invading the South.
Again, the salient point which you are unwilling to face is that the North wasn't attempting to march down to Richmond Virginia to free any slaves. They just didn't. You are just lying to yourself if you believe that.
...Notably, the preliminary Emancipation Proclamation was issued 16 months after Sumter...
Over a year later? What had the Union troops been told in the meantime? What was their stated cause before he spent a year polishing his proclamation? Surely they had to have been told some reason for being sent to Richmond.
Also, as of August 22, 1862, Lincoln was saying that no freeing of slaves would also be acceptable to him. My friend, this is the smoking gun which puts the lie to your theory that the North invaded the South to destroy slavery.
They invaded to stop independence and then they "moved the goal posts."
I would be interested if you could find somewhere, anywhere, that I said, “the North invaded the South to destroy slavery.”
The Union side fought the entire war to preserve the Union. A convenient side effect of the war was that it destroyed slavery. In fact, once the war started there were only really three options with regard to the institution:
1. A quick Union victory would have resulted in temporary continuance of slavery, probably with increasing and gradually strangling restrictions. For instance, Congress could have, entirely constitutionally, prohibited commerce in slaves between the states. Shut up separately within states, the institution would have withered away.
2. A CSA victory would of course have resulted in slavery’s continuance for an indefinite period. I assume it would still have been abolished by the turn of the century or thereabouts, though quite possibly with some sort of nonsense about “apprenticeships” or such, as was tried unsuccessfully in the British colonies.
3. A long war resulting in an eventual Union victory. This would have inevitably resulted in abolition. No way the South gets to keep its slaves after starting such a horrible war to protect slavery. (That would have been the Union belief, anyway.)
CSA apologists often try a remarkably dishonest rhetorical trick. If one agrees that there were other issues than slavery involved in the regional dispute and the war, they think they’ve scored some sort of debating victory. But of course in the history of the world there has never been a war fought with unmixed motives. IOW, they try to erect the straw man that those who are not apologists for the CSA believe the war was ONLY about slavery.
To be fair, there are those on the Left who agree with them. Recognizing that the fight against slavery would have the US government fighting in a noble cause, (and we can’t have that) they insist that slavery was merely a side issue in the class struggle, or some such nonsense.