Islamic extremists believe that they are God's chosen, and their destiny is to rule the world and impose their religion on all. They have been fighting that war for centuries, and they will never give up that war until every one of them is dead. They are ignorant barbarians, and need to be treated as such.
Now, they are at war with the West, and will not cease that war as long as they are capable of continuing that war. We can stick our heads in the sand and pretend that the war does not exist, or we can fight them on our terms, and not theirs.
The attack on the World Trade Center was a wake-up call, and we engaged in that war. However, we got weary of fighting the war, and we unilaterally disengaged. That didn't end the war, it just gave our enemies the offensive, and now allow them to decide where, and when, the next battle will be fought.
It will be fought here, and hundreds, maybe thousands, of our people will pay the price for our utter disregard of reality.