My view on this is basically same as El Gallo's. It's also same as it was with the Damore/Google case.

Employers have certain rights for fairly pragmatic reasons and there's a time and a place for everything.

NFL have their shareholders, sponsors and customers to answer to first. And after that comes the players personal needs. Using the spotlight NFL and the team gives you for a personal protest that has nothing to do with the sport just isn't the place for it. Doesn't matter at all how valid that protest is.