The problem with these clowns who kneel during the anthem is they work for a private entity and have no right to break the rules of said entity. If they break the rules, they are subject to whatever punishment the private company feels is just, such as fining or firing.
The First Amendment doesn't cover private jobs or yelling fire in a crowded building without warrant. It pertains to the federal government and what they can and cannot do to those who speak out against them. It also pertains to religious freedoms.