If the CSA was indeed a separate nation, as they claimed, then they were giving aid and comfort to their country’s enemy, to the extent in many cases of burning bridges, killing soldiers, etc.”
What?
Lincoln and his leftist henchmen cared nothing about the Constitution or the Founders intent! Just like their brethren in the New England States in present day America...
Most of the Founders had fought in the Revolution. They handled the Tories a great deal more harshly than Lincoln handled traitorous CSA sympathizers.
Look, you can’t have it both ways. If the CSA was a foreign nation, as it and its US supporters claimed, then US citizens conspiring and/or acting to aid and comfort a nation at war with the USA were indisputably guilty of treason by the Constitution’s definition.
If the CSA was not an actual foreign nation, it and its supporters were among the “enemies domestic” the Constitution speaks of.
The Constitution is a very stretchy document. The Founders never intended it to stretch over a civil war. That’s why they allowed for civil rights to be suspended in time of emergency.