Donning the Cowboy Hat

Months ago I darkly speculated with Dr. Emile as to the American threat of a nuclear deterrant in the "War On Terror". I did the blog entry when Colorado Congressman Tom Tancredo (R) actually proposed one of my more vile conjectures as to the limits of American capabilities: nuking Mecca in response to a terrorist act. With a US Congressman already broaching the mad notion, the scope of a grimly imaginative "response" is constrained only by whatever resides deep in America's arsenal: it could be done with a "filthy bomb", detonated with a isotope laden sleeve (strontium-90?) insuring a radioactive half life deadly enough to kill any pilgrim attempting to visit for, say, the next couple centuries. And what would Islam then be without the Hajj? Gruesome, and despicable reasoning, to be sure -- but such an exercise can only, at its worst, be slightly ahead of the creative thinking curve going on in the bowels of the Pentagon. Think not?
WMD threat could spark American nuclear strike.
and:
Pentagon draft plan calls for preemptive use of nukes.

What is the psychological and strategic impact of simply making the threat, even if qualification and disavowal follow? Would it be a deterrent?