In the United States, flags can induce polarizing outcomes. The Confederate flag is held dearly in the deep Southern states (by some Southern citizens). Officially, we have the Star-spangled banner with the 50 white stars and all and that is flown around in major sporting events. I think flags are a good idea to have rallying emotions as long as something positive is coming out of it. But one flag that is close for one can be a symbol of hate for the other. So, it's a catch 22.

And then you have flags (like that of Iraq and Iran) which have a special religious statement/text printed on the center which invoke a lot of sentiments for millions of people. Such flags should be dealt with care and attention.