I will say though, that while I am more inclined to agree with the player's politics, I am also of the opinion that they shouldn't kneel. Not because I'm patriotic, but because kneeling solves no problems and is probably the least tactful thing they could do to try and attempt to get a message across. To the eyes of almost everyone that disagrees with them, they are literally protesting America.
And I'm on the opposite side -- like, I'm inclined to disagree with the players' politics in this case, but I think they're doing protest exactly right. It's nonviolent. It's not even that disrespectful. It hurts nobody but themselves (and the league owners, but they've always got that option to fire, so it goes right back on the player).
They're basically nailing it, in all areas except actually communicating their point. This was supposed to be about police brutality -- which again we could have a whole argument there -- but suddenly it's all about Trump. Kneeling during the anthem to protest justicial inequality? Brave. Kneeling to protest a president you don't like? Childish.
But it does bring up an interesting dilemma. Does the NFL, as an organization, have he right to define its own speech? On the one hand, players (assuming citizenship) have constitutional protections in place for their own speech. On the other, they're wearing an NFL uniform, they're employed by the NFL, they're representing the NFL. Does the NFL get to say "No, sorry, you can't do that or you're fired?"
I mean we've established that they can penalize players for celebrations that the NFL deems inappropriate. We've established that kneeling can lose you your job (see for reference: Tim Tebow). It seems a short leap to say the NFL can fire you for kneeling during the anthem -- just like they could presumably fire you for shouting during a moment of silence. We've established that certain political speech can be prohibited by the NFL (like a show-of-support for Dallas P.D. after the BLM shooters killed several officers at an otherwise peaceful protest, which the NFL deemed inappropriate and forbade). So.... where's the line, do you figure? Open-ended question to all.