People aren't tuning NFL out due to kneeling. People are tuning NFL out because it's bad.
United States Football League - Wikipedia
NFL vs MLB: Revenue, Salaries, Viewership and Ratings
TV ratings down, team revenues up: have protests really hurt the NFL?, NFL
Why NFL Ratings Are Plummeting: A Two-Part Theory - The Atlantic
NFL concedes that national anthem protests are hurting business - New York Business Journal
The NFL's ratings are down. But national anthem protests aren't the whole story. - Vox
TV ratings down, team revenues up: have protests really hurt the NFL?, NFL
Kneelers didn't hurt NFL ratings before, and won't now
Floyd protests may affect NFL ratings, advertising dollars
They Realize the Bully Is Just Kind of an Empty Suit' - POLITICO
AP top sports story of 2017: NFL protests top the list – The Denver Post
Why the NFL cares about Taylor Swift and Travis Kelce – Orange County Register