I doubt that you can reason him out of a notion he wasn't reasoned into.
To my mind, the Founders were very clear in the Declaration about the causes that would justify rebellion.
Only ones that were intended to expand liberty.
Which to my mind excludes revolts with the primary goal of preventing the expansion of liberty.
Many though not all of the Confederates were honest enough to openly proclaim that they were by their revolt rejecting the foundational principle of the Declaration, that “all men are created equal.”
They were instead founding their new nation on quite the opposite principle, that all men are NOT created equal, that God and Science had proclaimed that some men must be forever enslaved to others.
I’ve always wondered how that would have played out had they won their independence. At the time, the idea was that they would hang onto the idea, in restricted form, as being “all white men are created equal.” Would they have been able to stick to that somewhat less than logical caveat, or would claims for superiority/inferiority within the white race soon have arisen?