what difference does it make if someone shows you a dozen tapes of him denying it?  Obviously he could just be lying as you would sure be quick to point out. Anyways, one could simply google 'bin laden denies attack' and you'd come up with a shitload of stuff from piles of established news sources. even defenselink.mil states it. They are even smart enough to use 'alleged' and 'suspected' of responsibility instead of proven or confirmed.