That idea was debunked within days of the attack.
No demonstration before attack on US Consulate, source says
"The intelligence source said no protests were happening before the attackers struck at about 9:35 p.m. local time last Tuesday. The account backs up claims by a purported Libyan security guard who told McClatchy Newspapers late last week that the area was quiet before the attack."
Why would Muslims demonstrate before 9-11. They would just go destroy something American on the day of celebration. I seriously doubt there were a bunch of Muslims sitting in an internet café a block away trolling youtube for anti-islam videos completely unaware that it happened to be September 11th. There are thousands of videos to piss them off but they managed to find the ONE video that created by someone that could be thrown in jail to give the appearance that we will punish those who insult islam. A coincidence?