This issue has a long history, and I believe it begins with the DH.  In the AL, pitchers can bean players with reckless abandon if they so desire.  They don’t, of course, but many pitchers gained an advantage by being headhunters without fear of retribution when they step to the plate.  Roger Clemens is a notorious example of this.  When he was with Boston, Toronto, and NYY, he was competitive to the point of viciousness (this may have been the steroids, but that’s beside the point).  He never had to step to the plate after a vicious beaning and face the music.  

My thoughts on this are simple:  allow the players to police the game, not the umpires or the commissioner’s office.  Given the chance, if there’s a headhunter out there, opposing pitchers will nip that in the bud.  That’s why there are fewer beanball wars in the NL – because pitchers know they have to step to the plate and if they’re aggressive to the point of dangerousness, then they will have to pay the price.  Melvin is right about one thing – it will happen again one day where a batter takes a fastball to the head and is blinded or worse.  The same goes with a batted ball back to the pitcher, but you don’t see a movement to move the mound back 30 feet.  The point is that the players have had the policing of the game taken away from them.  Let them do their jobs, let them retaliate as they see fit – with no ‘warnings’ or whatever such nonsense Selig and the umpires may come up with next.