Unfortunately, it's pretty much a circular argument at this point.

The side arguing to close DCA down draws, as its argument, the fact that slight deviations in an incoming flight plan can send the plane into a number of attractive targets. And that the slight chance of intercept you get from doing this on an approach to BWI or IAD is better than the zero chance of an intercept you'd get from doing this on an approach to DCA. Implicit to this argument (I think) is the fact that DC targets differ from other city's targets because you have the potential to cripple the nation's government depending on the severity of the attacks.

The side arguing to open DCA back up draws, as its argument, the fact that the ability to hit targets in other cities is still present (as evidenced by the tragedy in NYC) and that if airline security measures are designed to be safe they should be safe everywhere, not just 'everywhere except for DCA flights'.

Now, there are some side arguments. Some argue that the airport is intrinsically unsafe even without terrorist threats. That the runways are too short and the approach is too difficult. That the accident potential is present. Others argue about the blow to the DC economy. About the potential loss in confidence that arise from having one out of hundreds of airports deemed 'unsafe' despite similar availability to security measures.

I wish Bush would have addressed the closing of DCA in his recent speech at ORD. Then again, I have a feeling he just would have noted concerns about the flight plans over the Capitol.