Perhaps more to the point is the fact that we are fundamentally defenseless against motivated martyrs. Israel has far more experience in wars against terror than we do, and we can see their successes every day now. Surely if they just eliminated Arafat, their worries would be over.
Oppenheimer described America's reputation for fair play as our first and strongest line of defense against potential terrorists. Hijacking planes is an act of desperation - of taking a grievance to the only arena where it might be heard. For the sake of security, if not for the greater purpose of human rights and justice, we MUST support alternatives to violence. Evildoers would have no influence if aggrieved peoples could peacefully petition effective institutions of justice. Those who have cheered the attacks against the US are not bloodthirsty, they're just thirsty.
The truth will remain true in spite of our wishes to the contrary. Those institutions who find themselves in conflict with the truth will find it exhausting to maintain the conceit that war could possibly deter terror.