One of the closest things to a cogent argument that I'd heard was the "But Lincoln suspended habeas corpus!" canard. Perhaps on the surface, that argument is on point, but on closer review, it doesn't hold water (no pun intended). To emphasize the point, I would direct you to Jonathan Zasloff's post at The Reality-Based Community. I don't want to take too much of his post here, because it should be read in its entirety, but his summary is crystal:
Had Bush and Cheney really believed that there was an emergency requiring torture, they would have 1) said so publicly; 2) taken responsibility for the decision and defended it; 3) gotten Congressional approval; and 4) limited it as much as possible.
But they couldn't have done that, because torture was never about a national security emergency. It was about proving an Iraq-Al Qaeda link for political purposes. Or establishing precedent for unilateral executive rule. Or about military dropouts and draft dodgers like Bush, Cheney, and Addington showing how tough they were. Or something.