The only acceptable answer as far as I'm concerned is that it is never acceptable to kneel during the anthem.
Limbaugh claims that the players have the owners over a barrel due to their talents for playing NFL football. I think that is a bit overstated. The separation between a player that is chosen and one that is almost chosen cannot possibly be that drastic.
There may be a greater separation that occurs later on due to experience.
But any player gets better with experience.