No, it does deserve the vitriol. The South is not inherently bad and needs a better thing to rally around. The battle flag of a treasonous rebellion fighting to continue to exploit and harm an entire race of people for monetary gain shouldn't be it.
Stating a fact isn't the same thing as demonizing.
The Confederate flag represents a group of proud racists.
The cornerstone address literally contains "Our new government is founded upon exactly the opposite idea; its foundations are laid, its corner- stone rests upon the great truth, that the negro is not equal to the white man; that slavery — subordination to the superior race — is his natural and normal condition. This, our new government, is the first, in the history of the world, based upon this great physical, philosophical, and moral truth."