I'd be careful with invoking the Declaration of Independence against the South and making allegations of blazing ignorance if I were you.
The Declaration of Independence has the great statement, "We hold these truths to be self-evident, that all men are created equal ...," but it also contains the complaint against the king, "He has excited domestic insurrections amongst us ..." The insurrections referred to the freeing of blacks (and indentured servants) who would escape and serve the king against the American colonists. (Lincoln’s Emancipation Proclamation wasn't original.)
Lord Dunmore, Royal Governor of Virginia, had issued a proclamation in 1775 freeing slaves of the rebels. This was what the DOI was referring to. Here's the 1775 proclamation:
And I hereby further declare all indented servants, Negroes, or others (appertaining to Rebels) free, that are able and willing to bear arms, they joining His Majesty's Troops, as soon as may be, for the more speedily reducing the Colony to a proper sense of their duty, to this Majesty's crown and dignity.
-- Lord Dunmore's Proclamation [Governor of Virginia, November 14, 1775]
In other words, the Declaration said all men are equal but leave our slaves alone. In that sense the Confederates were for the complete Declaration while the North was only for part of it and assumed the role of the king and his officer, Lord Dunmore.
Jefferson very probably believed that "all men were created equal" should apply to slaves. But the words in his draft of the DOI were changed by the Continental Congress.
The Continental Congress removed Jefferson's charges against the king that "He has incited treasonable insurrections of our fellow citizens …" and replaced it with "He has excited domestic insurrection among us …" The Continental Congress probably didn't consider slaves as fellow citizens.
The Continental Congress also removed the charges against the king in Jefferson's draft that "He has waged cruel war against human nature itself, violating its most sacred rights of life and liberty in the persons of a distant people who never offended him, captivating and carrying them into slavery in another hemisphere, or to incur miserable death in their transportation thither." Why would the Continental Congress take that out if they felt that "all men are created equal" applied to slaves?
By the way, I'm all for those statements above as Jefferson originally penned them.
Ironic that Lincoln, in placing himself in Dunmore's posture generations later, took exactly the same measure to impose the yoke on Virginia that Dunmore had.
Lincoln just had a lot more soldiers than Dunmore; but they shared the view that overwhelming military power could bring Americans into line and show them their place.
There's no evidence of that, or that Jefferson had any real issues with slavery. Had he been pressed the I've no doubt he would have said he was talking about free men and not slaves. And most of the men at Philadelphia then would have agreed with him.
or perhaps they were telling the king that rather than solving the question with civil unrest and strife they could eventually and peacefully end slavery when they could. For example, by later passing the Northwest Ordinance.
Why would the Continental Congress take that out if they felt that "all men are created equal" applied to slaves?
Because they needed to come up with language that all the States would agree upon. They felt the Declaration had to be unanimous if it was to be.
Jefferson very probably believed that "all men were created equal" should apply to slaves.
You make my argument for me.