You really think they want to prevent something of the sort ever happening again or something? Puh-lease. Business has been booming ever since 9-11. Look at the past: every time America faces a serious recession (let alone a depression), they look for a war to boost domestic production. Of course, in the past they didn't rely so much on prison labour for for that wartime production and we weren't such a debtor nation- but old habits die hard.
The American power elite would love nothing more than another 9-11. It would boost the administration's ratings, it would silence the cries for a balanced budget and justify not only a continuation but further ramping-up of military spending, and provide another nationalist rallying cry to unify the American population against an outside threat (a vacuum left with the dismantling of the Taliban and of Al-Quada as an organized force and the death of bin Laden) and settle (even temporarily) the infighting among the constituency and redirect the people's rage from the government to [insert terrorist group here]. Oh, and it would justify the TSA, DHS, the next USA PATRIOT extension (certain privisions are set to expire in May 2015, IIRC, so expect them to create a reason for that to not happen)
So you see, abso, preventing another terrorist attack is the last thing they want. Let the arab world be mad. Nothing would be better than another attack and if one of your neighbors does it (or gets caught trying to), we don't have to do it ourselves. So please, tell them to go ahead and make it that much easier for us.