The crowd is angered about an incredibly stupid film that insults Islam and the Prophet Mohammed. The film is a personal statement, privately funded, that depicts nasty things.
This film may have been sufficient cause for the angry reaction taking place in a situation where American constitutional freedoms clash bluntly against religious beliefs. Protesting it is perfectly fine, what is not fine is to turn to violent actions or to call upon the power of the state to censor unpopular speech.
The world doesn’t need all this. Vicious people and violent conduct.