If is a disheartening event when someone has been the victim of racial abuse, but still offence is never given, only taken. Sure, you can try to offend people, and if you do try to give offence to someone based on race you're scum, but taking offence is the reaction of the person. People shouldn't take offence at the existence of a historical flag and if they do I'm afraid the onus is on them to deal with their problem; put less eloquently, grow thicker skin.
As for the racists, they'll see it the same way they see everything, through a lens of racial hate, paranoia and outright insanity "aw, those fuckin' niggers taking our flag! Aw, those fucking nigger loving ministers defacing our flag! What? You disagree? You nigger loving Jew!" Etc. They're insane people, we shouldn't let crazy, deluded, insane people bog everyone who is sane and has two brain cells to rub together down because crazy people see things a different way to the rest of us.