Some people are idiots.
The Confederates weren't fighting for "freedom" - they were perfectly free, as free as any other states of the Union (actually, probably more so, since they were imposing their pro-slavery policies on the free states), but were just upset that they no longer had control over the federal government.
It wasn't a rebellion over freedom - it was the equivalent of a spoiled brat deciding to take his ball and go home when the other kids didn't want to let him decide the rules of the game (even though the other kids helped buy the ball). Of course, this spoiled brat was fighting for the so-called "right" to own other human beings, to buy and sell them as they pleased, to force free men into slavery, and to continue to allow them to torture, rape, and murder these people for no other reason than because the owners were too lazy to do the work themselves. This wasn't even in dispute at the time - the rebels themselves said they were rebelling ONLY because of slavery; they even said that anyone arguing that slavery wasn't the SOLE cause of their rebellion was wrong. They admitted this of their own free will, trumpeting it to the world, and they also made no secret that they viewed slavery through the lens of white supremacy.
Decades later, the descendents of these rebels brought the flags of the Confederacy back, putting them up in public and protecting them with the force of law. Do you know why they were doing this? Because, at that time, the descendents of the people they kept as slaves were demanding the same basic human rights the white population enjoyed.
The Confederate flags have ALWAYS stood for nothing more than slavery, white supremacy, oppression, and violence. They are the American equivalent of the swastika flag. As far as I'm concerned, anyone who chooses to fly one is no better than a Nazi, and deserves nothing less than the same scorn and ridicule.