A new WorldPublicOpinion.org poll of 17 nations finds that majorities in only nine of them believe that al Qaeda was behind the 9/11 terrorist attacks on the United States.
...and bear in mind this is probably with the full knowledge that OBL and AQ have taken credit for the attack.

People don't believe things because of evidence or "truth". People believe things because it benefits them to do so. Here lies one of the gaping holes in the ideas underpinning "information operations," or "military influence."

If perception is reality, then the reality has to be recognised as one beyond any collective control, unless you are prepared to use apply some type of coercive pressure so that those you seek to effect, do so because they have no other choice.