Yes, they should be used if all else fails, and that intelligence is needed to save lives and/or avert a war and/or avert other truly undesirable outcomes. But the use of such techniques can always go too far -- people will be in charge of them, people will use them, and people aren't perfect. In fact, some are downright bounders. No matter what controls are placed on use of such techniques, inevitably somebody, somewhere will find a way to evade those controls and do something really evil. The trick is to minimize such abuses of power.