I've always done what I've felt like doing. If it was such a big deal, we'd do it each night before we went to bed and before eating lunch. I don't think having been or not been in the military has much to do with it. I love America as much as the next guy, but my history degree has taught me that sports and nationalism go together like bees and honey.
I say if you were the photog with the credits to cover the event then it's ok to move about in a discrete manner as needed to capture the emotion of the event at hand. It's no different than the military photographers I have worked with capturing the moments during the national anthem for anything they were called on to cover from retreats, funerals, memorial/veteran's events, etc. Just always do it without becoming the subject of attention!
