The legend of the Confederate leader’s heroism and decency is based in the fiction of a person who never existed.
The white supremacists who have protested on Lee’s behalf are not betraying his legacy. In fact, they have every reason to admire him. Lee, whose devotion to white supremacy outshone his loyalty to his country, is the embodiment of everything they stand for. Tribe and race over country is the core of white nationalism, and racists can embrace Lee in good conscience.
The question is why anyone else would.