This crap about the protestors being insulted by some obscure film is dissembling bullsh*t concocted by the western media to conceal the fact that these are islamic mobs celebrating 9/11.
Your explanation is probably the closest to the truth.
You are right.Muslims are striking against the U.S. in Egypt and Lybia on 9/11 to celebrate that anniversary. Obama supports Islam and Obama is an enemy of the U.S.A. Obama issued an Executive order giving Amnesty to a million illegals. this is an unlawful act. Obama is acting like a dictator and has buried the U.S. in debt. The goal of Islam is world domination. It is a great evil:
Islam, as it is taught in the Quran (Koran) and lived by Muhammad, as is reported in the Hadith (Biography and sayings of the Prophet) is a religion of Injustice, Intolerance, Cruelty, Absurdities, discrimination, Contradictions, and blind faith. Islam advocates killing the non-Muslims and abuses the human rights of minorities and women. Islam expanded mostly by Jihad (holy war) and forced its way by killing the non-believers. In Islam apostasy is the biggest crime punishable by death. Muhammad was a terrorist himself therefore terrorism cannot be separated from the true Islam. Islam means submission and it demands from its followers to submit their wills and thoughts to Muhammad and his imaginary Allah. Allah is a deity that despises reason, democracy, freedom of thought and freedom of expression.