CTE Linked To Football?

I recently watched the Frontline documentary, League of Denials. It explained that

scientists believe that football is likely linked to long term brain diseases. Studies show that almost every NFL player who complains about symptoms of brain diseases has CTE. The NFL was very deceiving and defencive in there approach to deal with this issue. Commissioner Roger Goodell deflected or declined to answer almost every question asked to him by reporters and by the United States government. The NFL funded studies of their own. When these results showed that there was likely a linkage between playing football and suffering these injuries, they hid them under the carpet. They had faulty studies and false results published in magazines to try to argue that there was no linkage. When it came to the research of the medical community, the NFL fought it every step of the way. Whether it be mistreating the doctors and scientists or persuading families not to donate the brains of the deceased NFL players, they did it all. Anything they could to deny and shootdown valid research, they did it. They were more interested in preserving the sport as they feared that parents would stop letting their kids play football and thus diminishing the sport and the NFL. They didn’t care that the sport may actually be lethal to its players.