It wasn't the death toll of 9/11 that mattered. As horrific as it was, that many people die in traffic accidents in under 4 weeks. Rather, it was the collateral damage, both in terms of actual physical damage, and damage to the economy. The physical damage was well into the tens of billions. Estimated cost to the economy was $1 trillion. Now imagine a few attacks like that each year. I didn't like a lot of Bush's policies, but at least they kept us safe. And I question whether some of them were even 100% necessary, or just an overreaction to a horrible event. But right or wrong, there haven't been any major attacks on American soil for over 7 years.
What I really fear from an Obama administration isn't socialism or Keynesian economics. In fact, it seems he intends to govern from the center if his inaugural address is any indication. Rather, what I fear most is that he'll be so caught up in the economy and other domestic affairs that he'll lose sight of his duty to defend the shores. His policies could work all the economic magic in the world. All you need are one or two suitcase nukes detonated in major cities, and it'll all be undone before the mushroom clouds dissipate. Keeping us safe matters above all else. If he can do so by making us less hated in the world so radicals don't have popular support, then wonderful. But if diplomacy fails you need to be prepared to do what is necessary, unpopular, and ugly, in order to preserve the nation. Whether or not his idealism can accept this harsh reality, I don't know. That's what really scares me.