Under the Geneva convention, a terrorist could be shot...
Just think of torture as emphasising the point that either you give us your information or you die.
They get what they want: To live.
We get what we want: their info.
Note, their status would change if they were to put on uniforms and pretend to be real soldiers.
Then we couldn't torture or shoot them.
you are making a mistake in thinking that the normal geneva rules of warfare apply to terrorists.
(Maybe the left should demand a new geneva convention be held to discuss this topic.)