If your grandpa always hangs his flag he is a true what?

I guess it depends on the country you and he live in. I know in some countries the flag is seen as a really positive thing but where I live it can be seen as a symbol of nationalism that borders on racism, and of imperialism.

I remember seeing our national flag flying in public once and I had a sharp intake of breath and my first instinct was that someone is going to pay for that. Post-empire guilt, maybe.