2) Comparing violence instigated against an oppressive government (perceived or actual) with that instigated against generic vulnerable individuals seems sort of specious. Arguing for a marketplace of ideas while opposing GoDaddy's decision to cease carrying on business with a particular purveyor of ideas seems contradictory.
3) I really can't get with your idea of comparing past struggles for human rights (which expand liberty in the aggregate) with exhortations to rape and murder, which severely abridge it. That's not merely absurd, but obnoxious.
By this logic democracy isn't worth it. Should we succumb instead to the wishes of strongmen willing to use violence in the name of pacifism? It is not by accident that one of the first things to go when a totalitarian regime takes power is freedom of speech.
1) People are not automatons and they don't carry out orders exactly as given. At best you can say speech confirms their pre-existing convictions.
2) Not all forms of violence are considered morally reprehensible and this definition changes over time. For example most Americans don't consider the revolutionary war to be unjust - despite its proponents calling for the death of British soldiers.
The decision of what is just violence needs to be subject to the market place of ideas. If it were not we'd still be in a feudal system - most regime changes come about with violence. This is also why speech advocating the abolition of free speech must also be tolerated.
3) Speech about taboo subjects is necessary to explore the hypothetical. Current ideas of human rights were in the past taboo.