Well, since Lee and others never pledged themselves unconditionally to the authority of the US government, their decision to secede from the "union" was not an act of treachery in any real sense of the word.
And to characterize the war between the north and south as "the war of southern aggression" is frankly bizarre, since it was the north that invaded, devastated, and subsequently occupied the south, and not the other way around.
Furthermore, the mere act of seceding from a political union, which was originally assumed to be voluntary, can never be rightly characterized as an act of aggression, anymore than leaving a church or a club can be.
Other than that, your post is spot on!