Nonviolent Protest and Resistance Privileged

[Crunchy]

It's a question which has occurred to me before.  At what point does oppression become bad enough that you need to fight back with more than words?  At what point do you abandon working within the system and seek instead to overthrow it?

We can all come up with situations in which the oppression is so bad that violence could be considered self defense but I don't think that's what is being asked here.  

I believe that many people are willing to go violent at protests because violent people like an excuse to justify the violence they want to engage in, not because their cause actually justifies it.