Part of the problem is that the Confederacy was invoked a lot during the civil rights movements (when a lot of statues go up and state flags get the stars-and-bars on), and a lot of people in the South decided to make the Confederacy - a thing that existed for a mere four years and lost - into a big symbol of the South. Which then sticks, because you've told generations of people who grew up hearing that Their Heritage Is The Confederacy while the exact reason why ("yankees telling us to let [racial slur] near our daughters").
It's similar to empires being the heritage of chunks of Europe, except the empires lasted a long time and during them there was art, science, exploration, social movements, fashions, colourful historical figures etc, the sort of things countries do take pride in as being part of their heritage even if it objectively happened cheek-in-jowl with bestial acts. And the Confederacy has none of that, because it couldn't, because it existed for solely four years and lost and it lost under the ideology of "landowners want slaves". It's like trying to claim Vichy is the key part of French cultural heritage and actually there was some great nuance going on.
It's similar to empires being the heritage of chunks of Europe, except the empires lasted a long time and during them there was art, science, exploration, social movements, fashions, colourful historical figures etc, the sort of things countries do take pride in as being part of their heritage even if it objectively happened cheek-in-jowl with bestial acts. And the Confederacy has none of that, because it couldn't, because it existed for solely four years and lost and it lost under the ideology of "landowners want slaves". It's like trying to claim Vichy is the key part of French cultural heritage and actually there was some great nuance going on.