“When Stevens finished his final meeting of the day, he escorted a Turkish diplomat outside the main entrance of the building. The situation was calm, the officials said, and there were no protests. Five U.S. agents and four local militiamen were providing security. A little more than an hour later, around 9:40 p.m., everything changed.”

There was no protest; just an attack. The video had nothing to do with it.

http://news.firedoglake.com/2012/09/24/libyan-people-protest-drive-militias-out-of-major-cities/

This resulted from protests to take back the streets, which ended up with 14 dead and 70 wounded, but which succeeded in moving out the militia groups. The Libyan government vowed to disarm the militias, but that carries less weight than the actions of the public. The protests enabled the state military to take over those militia bases.