“Just how deep did the rejection of the Founding Fathers go with those in the south in the 1800s?”
Rejection? Plenty of the Founding Fathers were Southerners. And Southerners in the 1800s took the Founders at their word, especially the Declaration of Independence.
To my knowledge the Founders were not popular among slaveholders. If you have specifics, I would love to see those. Names, dates, speeches, paragraphs. We cannot trust the historians.
Some of the more prominent names who were in on these were John Pettit, who called the Declaration’s “All men are created equal” statement to be “nothing more to me than a self-evident lie”. Pettit is written about specifically by Lincoln.
John Calhoun was among those critics, also attacking the all created equal idea in the Oregon Bill speech.
George Fitzhugh, one of the most prominent slavery propagandists anywhere repeatedly attacked Jefferson.
And Vice President Alexander Stephens also had harsh words for the Declaration in his Cornerstone speech.
The irony is that Jefferson in general and the Declaration in particular was the focal point of all this venom spitting, especially when progressives today try to paint Jefferson as king slaver.
That’s not what the slaveholders believed.
Again, if you have specifics please let me know I am interested to look at them.