I think that the talk of "lone wolf terrorists" is to divert attention from the fact that there are large, well-funded, anti-American, anti-Liberty, anti-capitalism, anti-Christian, anti-Jew, pro-Islamofascist groups out there who will try to pull off another attack the size of 9/11 or larger.
Yes, lone wolves, like Hassan, will pull off small attacks. However, the real fear should be those who want to bring down this bastion of Liberty with a spectacular attack. Lone wolves from within are the proper purview of law enforcement and should be handled with law enforcement tactics. Large-scale threats which, with near exclusivity, emanate from without, are the proper purview of our national defense structure and should be handled with military techniques.
The biggest problem that we have today in dealing with terrorists is that our leadership is too willfully ignorant to see this distinction.
All that said, the OP has a good point. Had the folks at Fort Hood been armed, they could've easily dispatched Hassan with many fewer casualties. Oh...wait...it was unlawful for them to be armed.