Well C4, as I've discovered, I'm one of the few on here that actually has fluency in the Arabic language, and has travelled extensively throughout the Muslim Arab world, taking my family with me, and enjoying the hospitality of countless Muslim Arabs in their homes. As the only Arabic speaking Chaplain in the Navy, I also got some unique time with our detractors on the ground in Iraq. Started for me in 1991, so I'd say I've got about 18 years of direct first hand from the horse's mouth understanding of reasons for this war.
Its not Britney's underwear, obviously C4. That's one dimensional thinking again.
They are tribal, Islam is a religion specifically tailored for tribal cultures, and tribal cultures operate on honor and shame. We are not tribal, we have no shame or honor. When we help them, we shame them. When we overwhelm them militarily, we shame them. When the little guy scores a small hit on the twin towers, billions around the world rejoice - they share honor. Its not about foreign policy, oil, or any of the other crap spewing out of both sides of congress. We are the enemy and will remain the enemy as long as we are powerful, international, and shameless. You don't think like an Arab, you don't have an inkling how their world works, you have no idea their motivations, really.
Ever read an Arabic paper? If you could you'd discover that our foreign policies in the Bush administration were welcomed by the wealthy Arab nation states, but viewed as embarassing to the Arab people that the once world leaders now need the help of a foreign power. Iran actually had more respect for us (honor/shame) under Bush. Usama Bin Laden was ashamed to have US/CF Forces liberate Kuwait, and petitioned to have an all Muslim force push Iraq back. I've sat in numerous Sheikh/Imam councils where they were flat hostile to our presence, because they wanted to do it themselves - it was embarassing that we were helping them, and that they needed our help. Why don't you study the economic situation in those countries from whom Al Qaeda recruits? The older devoted want to go back to the traditional tribal culture while the younger.
It is sloppy to blame this on foreign policy or Jihad - it is far far more complex than that. And until we admit the complexity, we will be fighting this war a long time.