Whether we want to admit it or not, we've made some grave errors in prosecuting the war on terror over the last 8+ years. Seems to me that military tribunals would do nothing to repair our image abroad, nor our own feelings mixed though they are about the nation we've become.
Handling these terrorists in our own judicial system, which we claim is the best in the world, so close to where the horrific attack on US soil happened, is a powerful symbol. Sullivan's right to pit the calm, methodical, and fair process of an American court against the fear-based scramble to revenge that seems at the heart of the pressure (and yes fear mongering) of those who are pushing for military trials.
And he makes another good point that most will not want to acknowledge:
It will be a civic lesson to America and the world. It will show the evil of terrorism and the futility and danger of torture. It will be a way in which Cheney's torture regime can be revealed in all its grotesque excess at the same time as KSM's vile religious extremism is exposed for its murderous nihilism. That all this will take place in New York - close to where the mass murder took place - is a particularly smart touch.
The glow of the righteous victim is dulled when the victim's hand can be seen carrying out its own injustices. Those from the Bush administration fear civilian courts, perhaps even more than those to be tried do. And for good reason.