People originally didn't always stand for the anthem, and putting your hand over your heart for the pledge and anthem wasn't always the norm, either. Before WW2 kids used to do something called the Bellamy salute when they recited the pledge. It looked too much like a Nazi salute, though, so it was abandoned.

Anyway, all I'm saying is that patriotic customs will always be evolving, so it seems silly to be bugged by how people choose to show respect. If players are goofing around or looking at their phones or whatever during the anthem, then by all means criticize them. But what's wrong with showing respect in a different physical style?