This flag worship is so bizarre to me. Stand, kneel, lie down, run at full speed while taking a shit, who cares?
All this "you must do X during national anthem" is, is a meaningless dick waving act for the pleasure of the people around you. That's all it is, achieving nothing, but boasting rights of how sizable your nationalistic dick truly is.
Quoting George Carlin: I leave symbols for the symbol-minded.
I bolded the key part for you. This is not before their job starts. They are required to be at the stadium several hours prior to kickoff time. They are "on the clock" at whatever that time is. Also by doing something in a work uniform, even if it was during their off hours, you are representing the company in your actions.
One would think since they have the uniform on they are already “on the job”. Even when they are at practice they are “on the job”. Professional athletes don’t just work a few hours a week. It is also in their contract they have to represent the team in a decent manner.
Your boss is actually not allowed to just treat you like shit and fire you for made up reasons, but you would have to actually stand up for yourself and defend your rights as an employee rather than being so desperate to have a job you'll just lie down and eat whatever shit the boss feeds you.
Many states are “at will” work places. And thanks to an over population of workers in America employers really do not have any issues finding employees. Employers can terminate employment for no reason or any reason at all if they choose to.
Employers have the power, not employees. That is, unless you have a contract.
Stating that marketing is part of the job of NFL players isn't "semantics", it's the core of the argument. Players are paid to create a product that's appealing to fans. Most of the time, that comes from ability or excitement on the field, but it's not the only duty they have as part of the job - this is pretty obvious.
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Not quite - they can terminate employment for no reason, but not necessarily for any reason. Even in at-will states, there are a variety of for cause firings that aren't legal. To take the most extreme example, you can't fire someone for being too black.
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The NFL has a broad conduct policy that refers to "conduct detrimental to the league". That's a pretty broad phrasing that gives substantial discretion to the league in determining what's detrimental. It's entirely reasonable that owners and management would think that doing something that pisses off ~40-60% of their fan base is detrimental to the league.