It's not even the right flag. The rebel flag we see nowadays is a bastardized version of a battle flag that was flown incredibly briefly and not recognized by most at the time. The original was square because they were too broke to afford the cloth to make it a rectangle.

The more common version of the flag still included the symbol but on a white background which was literally to show the "purity of the white race" but then people were confusing it for the flag of surrender. Fitting, in my opinion.