The funny thing with people complaining that athletes or actor or comedians (Jimmy Kimmel recently) shouldn't voice their political opinion, is that they are basically shooting themselves in the foot. If public figures can't say anything because they are "only" entertainers/don't know enough about the subject/it's not their job, what does that say about the people commenting? If someone on TV can't say what they want, shouldn't comment sections be removed too? I thought these people were fighting for free speech.. oh.. right...
Anyway, as a european this whole thing is a bit weird. First of all, why do you have the national anthem playing before a game at all? We only play national anthems when two countries meet in a sport, not on club level.
Secondly, why is the flag and the national anthem automatically linked to the army, veterans and police etc. and not teachers, doctors, social workers etc.? It feels so brainwashy it's scary. Support the army no matter what, even though they send their soldiers to unnecessary wars and don't give veterans the help they need. If I would be completely pessimistic, there's something with the timing of Trump. He stirs up the beef with NK and then goes on a nationalistic/racist rant against the NFL. It reminds me of the "if you're not with us, you are against us" from George W. Bush before the Iraq war.
Thirdly, it blows my mind how right wing media spins anything. It's a fucking cancer you need to get rid off.