Where should we draw the line with violence in sports?

Last week we witnessed one of the worst displays of on-field violence when Kewan Platt clothes-lined his opponent.  While we see aggression in sports all the time, Platt's actions went well beyond the scope of normal aggression and could have resulted in far more serious consequences (thankfully, they didn't).  Where should we draw the line with violence in sports, and what consequences need to occur for a "zero tolerance" rule to apply?  Read more here.

drstankovich.com