A performer on a military base is constitutionally protected from punishment for kneeling during the national anthem, because that base is public and they're acting as a citizen. A member of the military may have other requirements, I'm not really sure.
A professional (as opposed to high school or college, where this argument doesn't work) football player is playing on private property in the employ of a private citizen. That citizen could (and does) have the right to fine their employee for kneeling during the anthem. This isn't true for HS or college players who, by and large, are not acting under a private citizen owner, but are normally playing under the purview of a publicly funded school.
To put it succinctly:
>And they are taking these actions on private property.
Yes, and that private property is someone else's (in this case regulated by the NFL) who can set rules as they see fit.
Right.
Which is why I wrote:
>If the owners have the guts, let them all fire the football players...
But if the owners don't fire them, then whatever. Not our business. Watch them, or don't watch them. That's your choice. Nothing more.
My choice is to not watch them, but that's only because I think American football is a stupid sport, and that watching sports is, in general, a mindless waste of time.
Now, if a guy or gal is invited to perform on a military base during a national holiday commemoration, then sure, they should be compelled not to kneel. But if we're talking about things happening on private property as a part of a private gathering, those people can do whatever they please.
If the owners have the guts, let them all fire the football players. That's their right. Either way, the only input we should have on the matter is to watch the football game, or to walk away and not watch it.