In the cases we're discussing, the US had the right guy, the guy who planned the 9-11 attacks, a guy smart enough lie.
Waterboarding got very useful information out of him, details enough to keep other members of his organization from killing people. I read your link and it doesn't support your statement since waterboarding works.
What makes my life and the lives of others more important than the wellbeing of those who want to harm said lives is their relentless efforts to force me and others to obey them on pain of death. If they value my life, wellbeing, and personal autonomy so little, then I don't value theirs at all. It's prevention of harm to myself and others. Is your life worth nothing? I don't think so. I'd waterboard some asshole to keep his friends from harming you or most other people.
One thing I never do is claim any sort of moral high ground. I don't have any emotional stake in claiming I'm better than anybody, so I don't play that game. I don't need to justify preventing someone from harming me or others, especially when they are trying to harm me for their own religious or ideological reasons.
Sher, in my opinion, waterboarding absolutely is torture. The claims that it isn't come from the legalese of definitions, but that aside, its torture. I also think that sending someone to prison for stealing cars or some other non-violent offense and them getting raped and beaten repeatedly is torture. Letting someone linger in suffering because the law won't allow physician assisted suicide is torture. Putting so much dowry pressure on East Indian girls that they commit suicide is torture. Most societies torture in these and other ways. Since they do, I really don't have a problem with torturing terrorists to prevent their organizations from hurting and killing people.
As for the ends justifying the means, a great many people in the world hold that opinion, not just my enemies. Maybe that's because it has some merit.
The article mentioning Maher Arar offers no evidence of his torture beyond his own claims, which or may not be true. The article doesn't address what reason the US had for deporting him to Syria. It's not a good support for the statement.