Well, I for one can and would use torture under the right (extreme) personal conditions
I assume you are thinking about revenge not the collection of intelligence? Things like revenge and fear are very good motivational tools often used to rally the masses but the ultimate goal of the situation we face is not to seek revenge. I think you already realize that, so don't take that as me thinking otherwise.
I certainly want the gathering of intelligence to be effective at stopping future acts of terrorism, however I believe violence often does nothing more than just breed more of the same, and I certainly do not want an endless cycle of violence. I can find examples where certain people claim water-boarding for example was effective. Are they saying that to protect themselves for the decisions they made or because it is true? Was it to confirm already acquired information or not, as others claim? Why did certain government officials and agencies destroy documents regarding the matter if they are so convinced that what they did was right and justifiable? As one document destroyer stated....because the consequences of making this information public were far worse than the debate about just water-boarding. I believe that is very likely the case and don't wish to rehash old debate to point fingers but rather decide the best course going forward. What we did was an experiment and I suspect many things were learned from it. I do not expect the politicians or ideologues to admit where they were wrong, I expect them to cover their own butts and egos so I tend to give more weight to information from others and sometimes just look at the politically motivated for instances where they inadvertently contradict themselves. What are the consequences of those actions? Was it necessary, and are there better techniques to achieve the desired goal which is not just preventing any single act of violence but to prevent the maximum amount of violence looking forward. If we want to teach people that something is not good for them or society, it is sometimes best to not do the very same thing you are advocating against.
I suppose the best guideline I can think of here is an old quote of mine “do unto others as you would have them do unto you”.
That is a great guideline. Much better than "an eye for an eye". Some live by an "eye for an eye" and then end up with no eyes.