Flying a non-USA flag alone in the US. Disrespecful?

Iam with you, used to drive me crazy years ago driving through my home town seeing all the Portuguese flags on cars and houses with no american flag. Especially those whom are collecting some of the many assistance "handouts" this wonderful country offers.
My parents legally migrated from Portugal before I was born. They are proud of their heritage, but have always flown the Red white and blue in the front yard.