"It don't mean a thing if it ain't got that sting." --Apologies to Duke Ellington.
It's a truism that if it does not protect offensive speech by offensive people, freedom of speech is trivial.
What happened when Islamophobic bigot Pam Geller organized a "Mohammed Cartoon Contest" is well known: two Muslims decided to elevate their offense to the level of bullets. They were promptly shot dead by security personnel who doubtless anticipated such an escalation, and probably with no small amount of relish.
The organizers, the so-called American Freedom Defense Initiative is listed as a hate group by the SPLC, and is certainly no cause I want to be associated with in any way. But their right to sponsor a gathering to express anti-Islamic sentiments in speech and in ink is absolute, and I would defend it with everything I could. It is also worth noting that the Westboro Baptist Church basically funds itself by promoting maximally offensive occasions for their vile hate speech and then successfully suing anyone who overreacts in civil courts, winning monetary damages for the abridgment of their freedom of speech.
That the AFDI fervently hoped for a violent escalation by the objects of their hatred is not something I know for a fact, but I would not lightly dismiss it. Of course, they themselves would have the self-discipline to react to a "Jesus Having Gay Sex With Dick Cheney Cartoon Contest" with words only, and no fists, bricks, or bullets? I would hope so.