There's a few assumptions in their logic.
- that torture is wrong,
- that it doesn't work,
- the fact that torture is taking place at all is a sign of an incompetent government.
What is not addressed is how the use of torture has helped our war effort in Iraq fail. Imagine that you are a luckless Iraqi picked up by US soldiers for questioning. You are beaten with a baseball bat (as has been offered on the record as having happened) by an angry US Army cook, then are let go after the determination that you don't know anything is made. So what do you do? You tell your family and friends. Then how likely are those same people to alert US soldiers to danger? Not very.
These interrogation tactics the US has embraced in an effort to feel tougher are backfiring. One day, historians will ascribe at least some of the failure in Iraq to abusive treatment of Iraqis. But not today.