Boxing and mma are perhaps sort of different because damage to the brain is assumed. Fighters are well aware that it is not healthy. You could even die inside the ring to be fair. With football people didn't really assume those same risks. Maybe the sport could live on, if you'd make it clear that it's just as dangerous as boxing, but then how many parents are going to allow their children to play football in high school?
Btw the comment section next to the article is kind of weird. People going on about how Hernandez is evil and shit. Maybe he was. I don't know. But one of the biggest symptoms of this type of brain damage is the inability to control rage. Given the timing of the murder he was convicted of, the brain damage must have already been there at the time. This makes even the question of 'guilt' very difficult.