[gffauwsm] Arguing against the air horn

The Obama administration's line about NSA surveillance seems not to be about stopping it, but putting safeguards such that surveillance is only used to stop terrorists, drug dealers, and child pornographers (air horn issues).

Assume that the government perfectly implements these safeguards.  (Cynically, a highly unrealistic assumption.)  Is this satisfactory?  It still sits uneasy with me, but I cannot think of a politically palatable argument to refute it.

The politically non-palatable argument is the socially optimal rate of terrorism (e.g., American Revolution), drug dealing, and child pornography is not zero.