What makes you think "there's no doubt it is an effective means of interrogation"? The argument against it (any torture) being an effective means of interrogation states that under such duress the victim (yes, victim) will say anything. When you couple that with an interrogator who is convinced the victim has certain information to disclose, and will not stop until he receives that information, it becomes a recipe for confirming the interrogator's suspicions, regardless of whether they are true or not. In other words, if the victim really DOESN'T know what the interrogator seeks, or knows to be false something the interrogator seeks to have confirmed, it is virtually impossible to get this across to the interrogator.