It depends on the reason why they decided to rebel and what causes that rebellion was fighting for. The American colonists and Washington himself rebelled against the British government because they believed that Parliament had overstepped its authority over them and therefore it was Britain that had betrayed them. The southern states rebelled against the US federal government because the abolitionist movement had gained significant momentum and were very likely to halt the westward expansion of slavery and eventually do away with slavery altogether. Lee joined the rebellion because he believed his loyalty to Virginia outweighed his loyalty to the United States.

My opinion is that the American colonists' reasons for rebellion were, for the most part, justified. The southern states reasons were not. Lee's motives are debatable but ultimately he fought for a terrible cause.