If he wants to force them to behave a certain way during public rites like the national anthem, why doesn’t he simply line up a bunch of dummies at the sideline during the music? If he puts helmets on his dummies, television cameras and fans can’t tell the difference.
Let everyone in the stands show kneeling players a sign of support during the national anthem. Salute them. It takes courage. You won’t be a son of a bitch.