this is why all confederate flags are considered racist:
"our new government was founded on exactly the opposite idea: its foundations are laid, its corner stone rests upon the great truth that the [black man] 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" Alexander Stephens, Vice President of the Confederate States, April 1861
The CSA was created to maintain slavery. This is a fact, whether this caused the war or not, is what historians and individuals can't agree on. So, those flags (all of the confederate flags) represented a nation that was created to maintain slavery on the basis that the white race is superior.
It is no accident that Confederate symbols have been the mainstay of white supremacist organizations. They did not appropriate the Confederate battle flag simply because it was pretty. They picked it because it was the flag of a nation dedicated to their ideals: 'that the [black man] is not equal to the white man'.
Re-purposing the flag to represent southern traditions and values, the way many southerners/and non-southerners have, would be akin to a German picking up a flag of the Third Reich, waving it with pride and honor, and saying it doesn't represent the Third Reich but bratwurst and beer. By doing that they dismiss history and suffering their ancestors caused. Ask almost any German today if they are proud of their WW2 vets and they will undoubtedly with no hesitation say, no.
We should take a lesson away from the German: We should always remember our history, that doesn't mean we should always be proud of it.