Years ago, when Vancouver made their run at the cup, I remember a Rafi Torres hit on a Chicago player behind the net, which concussed the Chicago player, and ended his season.  Can't remember the player's name. He wasn't a star.  Just a run of the mill brain injury on a Tuesday night in the first round.  The bandwagon rolled on. 

You can talk about the rules.  You can weigh a player's value at the box office like a commodity.  You can posit that they are fantastically wealthy (some of them) and that they know the risks.  But it's ultimately this:

I'm not comfortable watching people give each other brain trauma in the name of 'sport' or 'entertainment', no matter how many dazzling feats of athletic prowess you mingle in with it.