Express a negative opinion about the Confederate flag and argue that it is a divisive symbol that stands for hate and treason against the United States.
The flag is a rebel symbol AGAINST the United States, that is, supporting treason against the US, and has been adopted by hate groups across the country.  How does one say they are a "proud" American when using this symbol that stood for being proud to kill US soldiers?  Using "Southern heritage" as an excuse is fine if one is proud of pro-slavery ancestors.  War for state's rights, ya, if you want the right to buy and sell another human being.  This flag is the same as the Nazi flag, Japanese rising sun and now the ISIS flag... all losers.  You know it's offensive to minority groups, so why isn't that enough?