The exhibit that was attacked was called "The Muhammad Art Exhibit" and its main attraction was a contest for the best caricature of the Prophet Muhammad... complete with a $10,000 prize for the best entry. This contest was organized by Pamela Geller, President of the American Freedom Defense Initiative, in response to a recent conference entitled, "Stand With the Prophet in Honor and Respect." The purpose of the conference was for American Muslims to confront and discuss the violence done in the name of Islam and find ways to peacefully combat those spreading violence and hate. Geller's art exhibit was organized, it would seem, to antagonize the Muslim community.
Geller and her supporters argue that her exhibit was simply an exercise in free speech; fully protected by the First Amendment... and they are 100% correct. That being said, sometimes simply because you can do a thing, doesn't mean you should do it.
In most denominations of Islam, depicting the any visual image of the Prophet Muhammad (positive or negative) is considered a sacrilege. Geller and her supporters know this fact and simply went ahead with the event proving not only were they determined to exercise free speech, but also exercise the "cherished American freedom to do something stupid..."
Some of the images included in the exhibit consisted of Muhammad being impaled on a pencil; having a beard filled with snakes; juggling with decapitated heads; defecating and urinating on the Quran; and wearing a toilet-paper turban... just to name a few examples.
Make no mistake about it, organizing this type of event in no way justifies taking violent actions or committing acts of terror, but this is where we are in today's world. On one side you have an extremist group, Hell bent on violently forcing their world view onto others - and on the other side you have ignorant, antagonistic elitists who, in their own way, are extremists who feel their way is the only way.
Extremism has many forms... none of which results in any good.