I believe that while the standard currently used by US courts (http://en.wikipedia.org/wiki/Imminent_lawless_action) is not ideal in all circumstances, it is largely functional and has not caused a great deal of harm. In practice, the way it plays out is that it gives hate groups enough rope to hang themselves in the court of public opinion. See: The WBC.
And these things were also drummed up by years (or centuries) of propaganda.
You don't see too many people bringing Leopold II.. Except for a recent article which made me go "Yay ! Finally !"
In other words, if you believe in your freedom, you should fight for it, not try to convince others of the pragmatic values of having it.
Ideas (and videos, and guns) don't kill people. People kill people.
It has always been, and will likely persist for a very long time.
Utilitarianism be damned - not a single millimetre of freedom should be sacrificed in a vain attempt to limit that human tendency.
Nobody could convince someone educated in the consequences of war to rise up and fight their war for them.
Censoring free speach is never the right answer imho.