While unenforceable, the US Code says that people SHOULD stand erect, remove headgear, and place their hands over their hearts when the National Anthem is played or while the national colors are being presented/posted. That's the prescribed flag/anthem etiquette, and it has been our national custom for far longer than any of us has been around. When someone does the exact opposite as a form of "protest," it's pretty obvious to me that his intent is to disrespect those customs.