Defending the Confederate flag on public buildings is the wrong battle, for two strong reasons.
The first no win problem is about authority. This flag is a symbol of rebellion against the U.S government, the one that put down the rebellion. Slice it any way you want but that's the pertinent fact of history on this topic. Be amazed and grateful that only in America would this much tolerance of a rebellious symbol have been allowed for this long.
Second, no matter what it means to you, it means something bad to huge numbers of other people. Their perception carries the same value as yours and you can argue what it means and should mean endlessly with nothing achieved but harder feelings. In that regard it is not so different from a Nazi flag on a public building after all, perhaps in Fredericksburg or New Berlin...
On this front it is a social good sense and courtesy issue, like not wearing a swastika in downtown Auschwitz or driving an Obama bumper sticker to my family reunion. You lose and you look bad while losing.
Put the emotion and effort into something genuinely useful.
