If the NFL wanted to fire those guys....they could. They very easily could. There is no such mandate that an employer cannot limit the free speech of an employee on the job premises, in uniform, during work hours. In fact, the very opposite is true. They have every right to do so.
Trump is saying that if he was in charge of that business, he would fire them. The First Amendment says very clearly states that it is referring to "Congress" and not the private employer.
~Jeordam
Saving the Princess, Humanity, or the World-Entire since 1985