Nonsense, no Founder ever supported unapproved unilateral declaration of secession at pleasure.
Yes they did support disunion from necessity as spelled out in their Declaration of 1776.
They also supported "secession" by mutual consent just as they did "secede" from the old Articles of Confederation in 1788.
But absent necessity or consent, Founders like President Jefferson considered secession, for example when threatened by his former Vice President Aaron Burr, unlawful and had Burr arrested and tried for treason.
Rome2000: "the South was lied to about slavery and would never have ratified the Constitution if they had any hint of the upcoming betrayal by the Federals in DC."
But there was no lie, no betrayal and before 1861 the South was "the Federals in DC".
So their real problem was: Southerners then were Democrats and Democrats, then as now, go ridiculously berserk when they lose political power.
One reason Southern Democrats ruled in Washington DC before 1861 was: about half of Northerners sympathized with them and held Union more important than slavery.
So those Northerners voted along with Southerners on most issues, most especially in electing pro-slavery Presidents.
And it might have worked again in 1860 except that Southern Fire Eaters split apart their Democrat party, running a Southern candidate (Breckenridge) in opposition to their own Northern Democrat (Douglas).
The result was minority Republican victory.
Nobody to blame but themselves.
DiogenesLamp: "Pretty much sums it up."
Indeed.