The movie is a hateful, personal attack on Mohammed, the Prophet of Islam. Even the actors are saying they were tricked into participating by being told the movie was about another subject. The movie maker then added words to the sound track after the actors had finished their work.
The people in the Middle East who are rioting think the US government must have allowed the movie, since that is the way their old governments controlled everyone and did not allow free speech. AntiAmerican groups are taking advantage of this to stir up violence.
Many Muslims, in the US, Lybia, and other places are condemning the violence.
Extremists on both sides are making all the trouble. The rest of us need to stay steady and remember that reasonable people are trying to restore calm.
We can help by not joining in the hate fest.