Something I don’t really get or understand:

If you’re an American, why be anti-American?

Or in other words:

If I’m an American, why am I not allowed to be “proud to be an American”?

For example, there doesn’t seem to be a concept such as “American pride”. There is Gay pride, there is “Asian Pride” (popular when I was a kid), etc.

Shouldn’t people from a certain nationality, ethnicity, race, etc be proud of their nationality? Or where they came from? Or their ancestry?