I’m from Mississippi and spent 30 years in the regular army, and then got my PhD in military history so please hear me out.
Plain and simple Lee, and other serving officers who turn in their blue for gray, were traitors to the uniforms they wore and the country they swore to protect (Lee had worn his more than thirty years and had spent very little of that time in his home state. This does not include Jackson and others who were not on active duty at the time of succession.
I quite understand Lee’s aversion to lifting a sword against his home state; but that said I cannot see how in good conscience he could lift the sword against those he had served with. Better for him to have left the army and set in his rocking chair at Arlington.
Lee’s success against his country caused more than 300,000 deaths, both from the north and south, and bleeding southern manhood dry for generations.
My two cents.
Even late in the war, Lincoln had little success getting the loyal slave states to agree to gradual emancipation, let alone immediate emancipation, so it can be taken for granted that the resistance to ending slavery would have been even stronger in the seven states which seceded first, where the slaves either outnumbered or nearly equaled the white population.
Robert E. Lee chose loyalty for his state of Virginia and against the nation he had previously fought for and swore an oath to. You call him a traitor for doing so.
George Washington chose loyalty for his colony of Virginia and against the British King he had previously fought for and swore an oath to, fighting side by side with British troops in the French and Indian Wars. Do you call Washington a traitor as well?
If your answer is anything other than “but that was different!”, you’ll be able to knock me over with a feather.