He probably should have put some more thought into it and how it would make the people around him feel. I’m sure many (most?) people who fly the confederate flag don’t do so with bad intentions, but at some point, if you’re doing something that can be predicted to upset vast swaths of the population, then it’s incumbent on you to either change what you’re doing or admit that you don’t have compassion or empathy for vast swaths of the population and you hold that action above the real pain of real people.