His career in the NFL is over, even though he wants to play so badly as not only as the quarterback nor the star athlete of the team he would play for, but THE poster boy of the football (pee wee, middle school, high school, college, and professional, even when you're out with your buddies at a park or something). He's just that much of a narcissist, and believes he'll get the owners to see things his way with this lawsuit because he believes he's that great. This whole thing with the protests have always been there, for the lack of a better phrase, in spirit. What S#!* For Brains doesn't understand (or maybe he does) is he was the instigator in all this, and one of the reasons why the NFL is failing right now. If he really thinks that he's going to be THE one to come in and save the NFL from it's plummeting ratings, he would find out quickly that even more people will tune out at the sheer mention he's coming back (I can't even imagine how many would stop watching if he did).
The NFL is a business. Their goal is to entertain people. I don't think the vast majority of fans and viewers don't have a problem with players expressing their religious beliefs because it does have an effect on how they prepare for the game to a degree. That's as far as it goes with personal beliefs. Politics, bashing on the cops, the military, the flag, and the country are NOT permitted. Taking a knee is the representation of that today. Also, they are breaking a rule that the NFL has established (but hasn't enforced, obviously): The players, during the time of the anthem, must stand up, with their right hand over their hearts, with their helmets in the left hand/arm, and must face the flag. I understand the whole "the NFL would be violating the players' 1st Amendment rights". However, in a work environment, you do give up that right in exchange to provide services for your customer, so you can make a living and provide for yourself and, if you have one, your family. Also, it affects the people you work around as well, so you really need to be quiet.
Now your employers are not saying give up what you believe entirely because they understand their employees have their opinions when it comes to politics, and their okay with voicing your opinions on your own time. However, if you get into that stuff within your work environment, you begin to lose customers. It'll start out small, but if you continue it, the small number of customers will turn into masses over time. Throughout that time, the business will also begin to lose money as a result. Big or small, that is how business works universally, and that formula has never changed and it never will. Again, religious beliefs are an entirely different matter. As a matter fact, customers actually really like and respect that.