Trying to understand the NFL boos: Do "fans" want players to be seen & not heard?

My first thought when the Cowboys were booed and criticized for taking a knee while standing for the anthem was that the fans were racist. But then why are racists going to see mostly black NFL teams?

Kirsten Powers (CNN) raised a good point just now: if fans had even a tiny amount of respect for these players, wouldn't they be curious about how the players feel and what their views are? Instead, these so called fans want the players to STFU and entertain them. To be seen but not heard. Really, to even die for their entertainment (CTE).