How is it fair to the people who want to sign up for it that you're making the decision for them? There's no social ill conferred on the greater public by their decision, what's the reason for meddling in their lives?
If the NFL has known about the risks for years and continued with its business model, it should absolutely face lawsuits and financial ruin.
I agree with everything you said except "The general public shouldn't ..." That is a very dangerous method of thought.
I agree that it shouldn't be banned, but the risks is the thing everyone needs to hear first, they should be plastered everywhere.
I have no problem bringing bloodsport back if it's entirely voluntary and the public has an interest in it. What if two guys want to voluntarily duel it out to death? Why not build a stadium and let them?