I think you are missing the distinction between Colin, private citizen, who has a first Amendment right to say what he wants and to stand or sit as he sees fit, and Colin, NFL player, who is being paid a huge sum to play football.
Most people on the clock wearing the uniform of their employer know they will be fired if they cross the line of acceptable behavior for their job. Do do you want to go up to a McDonalds and have to listen to a 5 minute political rant before you can get a burger? Wouldn’t an employee who did that get fired? Colin is demonstrating how egotistical and privileged he is, thumbing his nose at the rest of the country “ you would be fired if you tried this, but I am Colin and well I get to make my own rules”.
Colin needs to be fired and banned from the NFL. The precedent cannot be allowed to stand or it will destroy the game. How do you stop it if next week some players bring towels that say “Blue Lives Matter” or some wear “Hillary” socks or sport “Trump” decals? How long before the fans start pelting Colin with who knows what?
A positive aspect of Pro sports is that it tries to unite people of all races and religions, rich or poor, young or old, to root for their team together as fans. Pro sports uses patriotic ceremonies to tap into our common identity as Americans. We certainly have a whole political arena to fight over all the divisive issues of the day. But most of of us pay $ to watch the game to cheer for our athletes, no matter what their color, and for an hour or two be immersed in a non-political arena.
Yes, Colin needs be out of football and soon.