I think it's easy to look back and measure him up as a bad man when you use a 2019 yardstick. Little is mentioned about his post-war efforts to encourage pacification of white on black violence, encouraging of all African American kids getting an education, and his denouncement of his own military education.
The history books should be accurate, and accurate all the way around. I ask you, what is the value of painting him a bad man if you don't also highlight his own public repentance for so many of those deeds.
My city has renamed several confederate parks, always highlighting that "Robert E. Lee fought for slavery" and "didn't want blacks to vote". Both are true statements, but you miss a huge educational opportunity and I believe a chance to teach a powerful lesson: Apologizing, rebuilding, unity, freedom - all of these things require an open and honest conversation about what happened. Lee had extremely complicated views on slavery.
His words: '''In this enlightened age, there are few I believe, but what will acknowledge, that slavery as an institution, is a moral & political evil in any Country. It is useless to expatiate on its disadvantages. I think it however a greater evil to the white man than to the black race, & while my feelings are strongly enlisted in behalf of the latter, my sympathies are more strong for the former. The blacks are immeasurably better off here than in Africa, morally, socially & physically. The painful discipline they are undergoing, is necessary for their instruction as a race, & I hope will prepare & lead them to better things. How long their subjugation may be necessary is known & ordered by a wise Merciful Providence.'''
In summary, I don't condone him. I don't think statues are appropriate. But erasing his full life with his post-war works and efforts is losing an opportunity to heal.