The thing I've noticed lately is that prominent people, politicians, businesses or sports franchises seem to roll over like whipped dogs to positions that seem to be in opposition with civilized, lawful behavior.
Well, sitting or taking a knee during the Anthem is still "civilized" and 100% "lawful" but I get your drift.
The issue is really one of the blue states, or more appropriately the blue cities being the bulk of the money, the power, and influence in these organizations. It's why something as "red meat" as "sports" can be co-opted by PC Leftist attitudes. Are the billionaire team owners being shunned at cocktail parties in NYC and SF? It's another version of the "Inside the Beltway effect" that erodes the commitment of some conservative politicians. And while the NFL has a more equitable money distribution structure than say MLB, and things that prevent a team from just throwing money at their roster of players to dominate like the Yankees sometimes do, even if it's shared revenues, the big city coastal teams still rake in the most dough.
Of course the flyover country red-state/red-suburb people definitely vote with their feet and their wallets, but it's a second-order effect, and it takes time. And add to that, those influenced by blue area Leftist Coastal attitudes, they can rationalize away things like TV ratings drops and loss of ticket sales for a time too, before the displeasure of the fans en-masse really starts to make the NFL pull back.
And then of course, there's the whole "ratchet effect" that usually works in the Left's favor, politically, and in the overall culture war too.
So maybe 2-3 seasons of falling ratings and teams forced to cut or not renew players who engage in Kapernack protests for #BLM because of massive fan displeasure, the teams and the NFL might stop overt displays of protest, but that still doesn't undo the time period they allowed it, and the overall shifting in the "Overton Window" etc.