Here's my opinion on this, NFL players are compensated athletes that are selected based on their talents. They have been blessed with family that supported them throughout their upbringing, education, practices, pop warner/high school/college games. At the beginning of every game the National Anthem is played and there was no participating player protests that took place despite what was going on in the world/country. They have fans that have followed their success and nothing could distract the game to carry on.
At that time, all the kids wanted to do was play the game, spectators and family wanted to see them play. I believe that a stadium that's a venue for the players and fans is NOT a FORUM to display/voice your political opinion. I understand that there is no policy/regulation/legislation that prevents anyone to protest under the 1st Amendment. I don't have an issue with that. Although, can we keep politics out of the stadium for just a period of time that the game is being conducted? Can we just set aside our differences of the outside world and focus on playing the game? Fans have paid for season tickets, spent time tailgating and just want to enjoy the day.