No, I wouldn’t compare anyone in the Confederacy to Hitler or a Nazi. I wouldn’t even compare Lincoln to Hitler. But you on the other hand worry me.
Perhaps his point is, the actions of a man are not so different when he is desperate. Hitler was a murderous bastard in 1934 when he had Ernst Rohm murdered, as well as before the last days, just as he was during the last days. As Nostradamus suggested of “Hister” “bloody his rise and fall shall be”.
Lee was known as a brutal slave master before the civil war. He selected his corps commanders based on their discipline, which in some cases meant willingness to impose very harsh treatment of his men, all for the cause of human slavery.
Slavery must be brutal because some do not wish to be slaves. When anyone accepts slavery they must accept the brutality.
To be fair to Lee, he was able to learn and adapt to circumstances. He was never accused of brutality absent the Confederate Army and absent Slavery. When he led the Marines at Chapultepec, he didn’t have a company of sharp shooters behind his assaulting element.