Protests: To Be Violent, Or Not To Be, That Is The Question...

Often times, we encounter or hear about protests.  Some are violent, some are not.  The question is, are non-violent protests as effective as those that are not?  Does it cause more discussion to inflict violence or does it simply cause people to feel cynicism and ignore the fight for a cause?  One protest  that most recently comes to mind is that of Occupy Denver.  It was incredible to see the mass amounts of citizens gathered around City Park, protesting for the things they believe in.  Besides the violence from police onto citizens, there was little violence.  Would this Occupy Denver protest have been more effective if citizen's were more violent and perhaps threw tomatoes at city buildings?  The definition of protest is: "A statement or action expressing disapproval of or objection to something."  So, if you want to make a bold statement and thus cause change, must you engage in violent behavior?  Or is there other ways of going about it....