One defense of the Confederate flag, made below, is that people who fly the flag and wear it on their tee-shirts aren't necessarily, themselves, racist. This is a rather low hurdle to clear. The harder test doesn't question your where your heart, but your sword.
From this perspective, the question isn't "Do you hate black people?" It isn't "Would you invite a black person to your barbecue?" It's "Are you more offended by black people who recoil in horror at the Confederate flag, than you are by the flag's history?"
It may well be true that Alabama's desire to fly the Confederate flag at the state capitol, or the desire of many Alabamans to use it themselves as they see fit, has nothing to do with the fact that the state was the last to drop its (unenforceable) prohibition against interracial marriage (in 2000!). It may be a mere coincidence that the only people to oppose the Alabama repeal were leaders of the states' "Confederate heritage group." But if the flag's defenders aren't racist (which I can accept) the necessary conclusion, while banal and common, isn't anymore comforting--a shocking ignorance of one's own history.
Well here's the thing: Historically racist often don't declare themselves. And when they do, they often claim to be acting in the interest of blacks and whites. Indeed the "not a racist" argument has been upheld, in varying forms, since the end of Reconstruction.