I, too, am allowed to wear any sort of political T-shirt, or whatever, while at work (as long as it is not obscene, or otherwise inappropriate), but I'm not sure that qualifies as an "action," per se. It certainly wouldn't affect my job in any way. Be that as it may, I have also never been asked to stand for the National Anthem while at work, and I'm not sure that I would capitulate if I were.
Also, wouldn't standing for the National Anthem be every bit as much a political statement as kneeling for it?