If there is an imminent threat, then follow up the threat. If it's only a vague "we think something's up" (like we're under now), then there's not a lot that can be done, morally and legally, except to remain vigilant. Interning the innocent and guilty alike would be as ineffective as it would be wrong.
Take the present situation. A suggestion has been made that hijackers might take over a flight coming into the U.S. from abroad over the next few days, and use that as a bomb as it makes its final approach into New York. All the rights infringements you can imagine wouldn't prevent that, just as it wouldn't prevent a (highly speculative) suitcase nuke.
You're a Physicist, you tell me.. that's not an "immediate hazard?"
As a physicist, I tell you that I doubt they even exist.
As a debater, you're disingenuous.
We were both speaking of hypotheticals. To now fall back on questioning the basis for the hypothetical is intellectually dishonest.