half the people who give them money.
#2 He will divide his organization. The players, the coaches, the owners are going to have to pick between publicly supporting his protest, having no comment on it, or being against it. They'll get asked about it every week as long as the media keeps making him a talking point.
#3 The last few times he was seen playing quarterback, he was playing really really bad.
That's a lot of negatives to risk for a guy who isn't even guaranteed to make a positive impact for your team.