I don't think the NFL is responsible for CTE considering these men have been playing football since they were in Junior High School, at what point is the NCAA not apart of the class action suit as they sent these amateur athletes over to the pro side as part of a partnership, a farming system if you will.
This is a violent sport and maybe the NFL needs to protect itself by adding a disclosure in their contracts stating they know and acknowledge the dangers of playing the sport as they for the most part are well compensated especially in this day and age if they perform well.