After watching the finished product, it's easy to see why. League of Denial is an exhaustive, years-long investigation into the staggering number of former NFL players now suffering brain damage, and how the league systematically misled the public about the connection between tackling and CTE (or: chronic traumatic encephalopathy, the primary brain disease that affects NFL'ers.) Because the NFL refused to cooperate with the film and its reporters Steve Fainaru and Mark Fainaru-Wada, the documentary comes off as an one-sided affair. However, it's not preachy. Seeing Hall of Famer Mike Webster stumble through interviews before his early painful death at 50 kind of speaks for itself.
You can stream the entire two-hour doc here without commercial breaks. It probably won't make you stop watching football—I won't, either—but League of Denial will almost assuredly go down as a milestone moment in sports history. You'll want to know what it says.