The NFL is not apolitical. Your customers were. The reason they turn away is precisely because the NFL has decided to become political for a while now, and leftist anti-American at that.
The NFL could have easily said: "We stand with the President, disrespecting the anthem is not ok, and by the way: our statutes don't allow for that to begin with, so starting right now, who kneels during the anthem will be fined."