When I see someone flying the confederate flag I am thankful that we have the freedom to do so, even if it means that others might be offended. I don't prejudge them as stupid.
Being thankful for freedoms, not offended and knowing someone is stupid are not mutually exclusive. I have, with my own eyes, seen a confederate flag flown next to a picture of a lynching. I personally hear people make comments about the war of northern aggression and how everything was fine before the war.
When I see someone flying the flag, I absolutely know everything I need to about that person.