I really do not want to get into it too much, but he raised his hand on the parade ground at West Point and swore an oath to support and defend the Constitution of the United States against all enemies, foreign and domestic. He did not swear an oath to Virginia. He did not swear an oath to support and defend the constitution of the US after defending Virginia.
I understand why he did what he did. I understand that he did what he thought was right. He paid for his “sin.”
But the oath he swore before God was the same one I took. It is the same type of oath you swear before God when you get married.
Do I think he was a traitor?
I think you confuse allegiance to Lincoln with allegiance to the Constitution. At West Point during that era they used Joseph Story’s Commentary on the Constitution to teach government. Story, of Massachusetts, taught what most Americans of that time believed, that secession was a right held by the States. Unsurprising since the New England states had flirted with secession in 1814 with the Hartford Convention.
Moreover the authority of States to overrule the national government was a belief expressed by both Jefferson and Madison in the Virginia and Kentucky Resolves which they authored in 1798. Those Resolves are a basis of the States Rights doctrine which was espoused by the Confederacy.
In a similar vein Jefferson Davis was never brought to trial for treason despite his repeated requests that he either be charged or released. Davis was certain that he had broken no law and it appears to be a belief shared by his captors who refused to charge him.
The belief in an all powerful national government is something that is taken for granted only after Lincoln. It was an era of triumphant nationalism and not just in America. Lincoln crushed the South’s attempt to leave the union. The German states unified. Italy unified.