Here are several reasons why:
1. The Confederate flag has evolved into a symbol of Southern pride for those that display it. Having lived in the South in various places for most of my 52 years, the number of times I’ve spotted one, be it an actual flag, a fake license plate, bumper sticker, etc., are few and far between. Why South Carolina’s state capitol chooses to fly it is a mystery to me.
2. Lack of empathy and not necessarily education. I have yet to see anyone sporting a Confederate flag that isn’t white.
3. It is still legal to display a Confederate flag in the US. This is where the comparison to the Nazi flag in Germany differs, amongst many other reasons. It’s an apples to oranges example.
4. There are bigger fish to fry. (See @bossob‘s post.) Here are some statistics from a Gallup Poll conducted in 2000. Americans Divided on Southern States Flying Confederate Flag