What isn't generally talked about in discussions is that no matter what he chose, Lee would be fighting against family. His family, like so many others, was divided. He had a sister who was a Unionist, and his nephew was on John Pope's staff. He had a cousin who was a Union Navy admiral and another cousin who was a Union Army judge advocate. He also had a cousin who was an aide-de-camp to George McClellan.Kind of late to the party on this one, but I'll add a few of my thoughts.
I happened to watch the discussion posted on one of the other threads - April 9 / Military Rivals: Grant and Lee - and a thought occurred to me why possibly Lee chose to fight for the CSA instead of the Union. Both had troubled relationships with their fathers, which I believe was the deciding factor for Lee's decision to side with Virginia and the Confederacy. Evidently, Lee's father, "Light-Horse Harry" Lee III was the Bernie Madoff of his day. Not only was he a swindler of sorts, and infamous for that alone, he abandoned his family. Reportedly, Lee, while attending West Point received no demerits throughout his entire attendance to the academy, which speaks volumes, as noted by one of the commentators.
In that Lee chose not to fight against his family and fellow Virginians seems to have been out of his deep sense of honor and loyalty to them, not to betray or fail them (unlike his father) in what he most assuredly saw as their time of dire need. Regardless of how we perceive his decision today, IMHO the facts based on this most esteemed aspect of his character is worth remembering and honoring.