There is one serious argument for this course: that a civilian court will provide greater legitimacy for the imposition of the death penalty than a military tribunal. But the guilt of these terrorists is not in question. And it is difficult to imagine that those repulsed or impressed by Khalid Sheik Mohammed's confessed crimes will care much about the procedures surrounding his sentencing.

Gerson seems to be saying in that last sentence that nobody actually cares about the rule of law.  That's not literally true, of course, but from the vitriol expressed toward the idea of  defendants having constitutional rights, you do get the idea that its stock is at a low ebb.