Because you said please.
No, I would not legalize torture in any form to be used in law enforcement. However, it is routinely done. (see my thread:
Is tasering torture?)
What differentiates that scenario from what our government and its agents have been doing to suspected terrorists
Enforcing rule of law is an entirely different matter from protecting a country during wartime. Do you want your cops killing gang members on the street? Of course not. Do you want your soldiers in 1944 shooting at Japanese soldiers, whose country's goal is to destroy the US? Yes you do.
It is inhumane.
To not do whatever you can to foil plots to kill thousands and hurt the country is inhumane.
It is illegal.
Ah, but the law is never so black and white...
It violates our Constitution.
Constitutional protections are not available for non-citizens who are not living in the US.
It's in violation of International Treaties we've signed.
I think this is true, but probably not important. I would expect that the authors did not consider the possibility of suddenly having to fight a shadowy network of combatants, scattered around every corner of the globe, some places which are signatories and some not.
It's proven to be unreliable.
I doubt it, and I'm sure all gathered intelligence is validated using sophisticated methods we can't even imagine.