They should be “mediated” right out of the league.
I haven’t tried to count tallies, but I think it’s only a small % of NFL players causing the problem. Many teams seem to have hardly anyone involved.
So it may well be only 10% (or fewer) of players protesting. Even among black players, who are 70% of the league, it is probably not much more than 10%. The NFL should have cracked down hard at the start of the 2016 season.