That makes sense to me, but then there's that "one guy" (not one guy) that is willing to push it too far and shifts the center of the sport towards the more vio

That makes sense to me, but then there's that "one guy" (not one guy) that is willing to push it too far and shifts the center of the sport towards the more violent end (e.g., Mike Tyson). The OP mentions this, for example there are stern rules in the NFL against grabbing a player's facemask and cross blocks, but they still happen frequently. Furthermore, the games rules reward pushing the envelope (15 yards vs chance of serious injury to e.g., the quarterback is unequal). You can make an effective argument that if you play football in the NFL you will sustain many serious injuries to your brain and body (as the OP does). I'd expand that to include college and high school football as well.