“It falls apart right there because many political leaders from Webster to Clay to Madison to Jackson to Buchanan to Lincoln..”
His argument does not fall apart. Your use of ‘higher authority’ political leaders is not relevant since the government was a representative republic, not an oligarchy of political personalities.
The Republic was governed by law, not the masses. There was no admonition against secession, nor consequence of enforcement ever vested in the central government.
OK, would it have been better to say that his claim that "Prior to the American Civil War, it was popularly assumed that states which had freely chosen to enter the Union could just as freely withdraw from said union at their own discretion" is completely false?
The Republic was governed by law, not the masses. There was no admonition against secession, nor consequence of enforcement ever vested in the central government.
Nothing allowing it either.