Ambassador's death result of political use of religion, not simple mob mentality
This isn't really a story about a trailer for a movie. It's a story about the use of religion as a violently divisive political tool.
The hate has a direction, and it has a political purpose, grander than a Youtube video.
Late at night on September 11, an apparent riot over a Youtube clip of a movie mocking the Islamic prophet Muhammad turned into a full-scale assault on the U.S. mission in Benghazi. By the time the night ended, four Americans, including U.S. Ambassador to Libya Chrisopher Stevens, lay dead.
It's easy to draft the narrative, 'Dumb Muslims freak out over dumb movie.' But there's a more complex narrative in these protests and all of them. Really, we're seeing a dangerous and all-too-frequent tactic by government and paramilitary groups: using people's most prized cultural beliefs about life and death and good and evil as a control and manipulation tactic. In these cases, hate has been fomented by agitators with distinct political purposes. The tool they used is an old one: religious belief.
Ansar al-Sharia is a militia with ties to former Libyan ruler Muammar Ghadafi. Its goal is to establish a government based in the political application of religious law.
It may have been wishful thinking on the part of the Muslims with whom Chris Stephen of the Guardian spoke, but the people who were there don't remember anything like a typical protest.  What they remember is a deliberate attack. Individuals carrying military-grade weaponry slipped through a mob creating chaos in order to assassinate an ambassador whose career ran parallel to the Libyan revolution to overthrow Ghadafi in 2011.
It's the narrative Libyan president Mohamed Yousef el-Magariaf has embraced. He blames al-Sharia, and has ordered it and other militia groups to dissolve and give up their weapons.  It's a touchy thing to embrace. On one hand, it could be an excuse to attack militia groups bent on undermining the newly-formed (relatively) secular government. On the other hand, it is a rather public admission that the Libyan situation is very much still a tenuous one, and that extremist groups can gain public favour.
The half-baked film is a small element. It is one more piece of propaganda Al-Sharia can use. A group that received generous treatment under Ghadafi wants its power back, and it wants more power, too. More than guns and more than grenades, the strongest tool it has is religion, and it appears to be making use of that tool. We hope it's a message to Yousef el-Magariaf to stay the course of separation of church and state.
Al-Sharia, for its part, prefers the simpler narrative. In a news release translated a few days after the killing, Al-Sharia representatives said this: “The Brigade didn't participate as a sole entity; rather, it was a spontaneous popular uprising in response to what happened by the West.”  Spontaneous, perhaps. But Al-Sharia members and others were carrying assault rifles and rocket propelled grenades, and the attack on the U.S. Embassy lasted four hours.
The protests erupting in other parts of the world over the film do seem more specifically aimed.  However, they include similar political underscoring. In Iran, for example, the chants sounded something like, "Death to the US" and "Death to Israel."  The video was shot in the United States, but by Coptic Christians, not Jews. Sad as it is to say, the protests in Iran could be over a number of issues, all spurred on by a government using its citizens' religious beliefs and fears to keep power.
 Chris Stephen interviews residents of Benghazi, the Guardian. http://www.guardian.co.uk/world/2012/sep/21/benghazi-raid-libyan-revolution
 Huffpost story about the dissolution of militant groups http://www.huffingtonpost.com/2012/09/23/libya-embassy-attack_n_1907252.html
 Clip from translated news release: http://www.longwarjournal.org/threat-matrix/archives/2012/09/ansar_al_shariah_issues_statem.php#ixzz27V5O2USA
 other protests: http://www.nation.com.pk/pakistan-news-newspaper-daily-english-online/international/25-Sep-2012/fury-persists-over-anti-islam-actions
 Iran protests: http://english.farsnews.com/newstext.php?nn=9106242266