He testified to congress that the video started riots that lead to the death of the ambassador... That lie to congress is a serious mark on Petraeus.. He should resign or be fired.
I have not done an extensive search, but the video excuse seemed to 'evolve' [Team Obama and MSM sure do like that word] in this manner:
In her remarks at the State Department on Wednesday, September 12, one day after the Benghazi attack, Hillary Clinton mentioned "inflammatory material posted on the Internet."
That statement may have given the WH an idea: Task some aides and underlings with Googling the Internet for inflammatory material. Someone found an obscure anti-Islam video. They 'evolved' the narrative to make the video the culprit.
By Thursday, September 13, Clinton was saying there is "no justification — none at all — for responding to this video with violence. We condemn the violence that has resulted, in the strongest terms."
And thus was born the video excuse.