The NAACP is a cesspool of ignorance.
Robert Lee emancipated all of his father in law’s slaves after his father in law’s death..
His family kept an illegal school for slaves on their Virginia plantation (it was illegal to educate slaves in Virginia).
After the war, he was in charge of enforcing slave emancipation in Virginia.
And we all know that the only reason Lee fought with the South was because of his allegiance to Virginia, not because of any affinity for slavery.
IIRC, Thomas "Stonewall" Jackson did also.
Not so much ignorance as falsehood.