Those who come (and pay) to see a game, concert, or any other non-political activity are a captive audience to such displays, and though most fans might agree with their sentiments, that's not what they came to see, and it's not what the owners (and indirectly, the fans) are paying the players or performers to do.  Whatever an owner does, fans are free  -  depending upon their attitude  -  to attend or boycott (or criticize) that decision, and/or that activity.