That's what they have been trying to convince us to believe for over 160 years, but the evidence indicates this is just a lie and that it is propaganda.
The Corwin Amendment (an Amendment to the Constitution to make slavery permanent in the United States) passed the House and Senate by greater than a 3/4ths margin in March of 1861. Abraham Lincoln himself called for this amendment to be ratified and did whatever he could to see that this amendment would get ratified.
There was no "moral" consideration for doing this. The reason the Northern controlled congress voted to make slavery permanent was in an effort to keep the Southern states (producing 700 million per year in the economy of 1860, most of which was controlled by DC and Northern industrialists/power brokers) under their economic control.
They didn't care about slavery beyond the extent it affected their power and their money. They certainly didn't care about the slaves as people.
There was no "morality" there. It was all self interest.
Keep in mind that the self interest you allege is all Democratic party. Only Demos owned slaves. Only they enacted JimCrow laws and fought the civil rights movements and laws.
And, despite the lies you misrepresent there was a morality component. The US was in a quandary since in order to not be in conflict with its premise that “all men are created equal” it had to officially say that blacks are not complete men. The founders knew this could not stand but they had to stay free of Britain.
Once the US was strong enough they rejected the partial man premise, which is a moral issue. Purely.
However, the Democrats never bought into that idea. That is why all of them still consider blacks to be “their property”.
“an Amendment to the Constitution to make slavery permanent in the United States”
“No amendment shall be made to the Constitution which will authorize or give to Congress the power to abolish or interfere, within any State, with the domestic institutions thereof, including that of persons held to labor or service by the laws of said State.”
The Corwin Amendment does not make slavery “permanent” in the United States. The Congress of the United States can still limit slavery in the territories and any State is free to abolish slavery within their borders if the wish to do so.