Whether or not you think waterboarding is heinous or crosses the line between interrogation and torture isn't really the issue here.
First and foremost is the fact that torture doesn't work. Someone will tell you whatever they can in order to get you to stop. Or just not tell you anything. Very rarely does the information gained from torture lead to actionable/useful intel. Mostly because, once you take someone off the battlefield and away from their network, they don't know what the hell is going on anymore.
If they were very high up, they've been replaced and plans have changed. If they were low down, they won't have much to say that is helpful or that you don't already know.
The notion that anything we did to our detainees prevented additional acts of terrorism is nonsense. It is already plainly evident that real "terrorists" have all the patience in the world and excellent planning ability.
For instance, US knew about Bin Laden and his network long before the first bombing of the Trade Center in 93'. That plan, with the bombs in the parking garage, it took years to conceive and carry out. When that failed, they took the next 8 damn years plotting their most magnificent attempt yet. They meticulously worked their agents into our country, WE TRAINED THEM, and when it was time they did their work.
Capturing a few guys at a time during the middle of a conflict and hoping to extract information about imminent attacks (happening within the same year or so) is ludicrous. Yet everyone seems to think that's how it works because they love to watch JACK BAUER do it every night on cable TV.
There are no Jack Bauer situations, that doesn't happen. Waterboarding some guys we picked up over the course of a couple years following 9/11 didn't prevent a damn thing. Terrorists don't operate on a schedule that would be so convinent as for us to grab one of them and foil all their master plans in a matter of months.
As if this isn't enough of a reason not to use those tactics, the fact is that they represent acts which the US would frown upon other nations for using. We have signed documents stating this and agreeing not to engage in them ourselves. Yet now we have, and we did so on the whim of panic, hoping to appease a nation which was all pissed off because no one had laid a finger on them since the 40's.
This makes us hypocritical every time we attempt to point the finger at another sovereign nation for something we disapprove of. We cannot waterboard and continue to tell others how they should conduct their state at the same time.