I suddenly want to walk into the united states and blow up your house for hearing you say this
Resolving our political differences with empty threats of violence? How pathetic.
"it's not 'technically' torture! we're just going to make your day really fucking suck in order to get you to talk" is bullshit still stands
Waterboarding does no permanent physical harm and causes neither "pain" in the classic sense nor lingering ill effects. Most damaging to your case though is that terrorists can end their coercion at any time by simply telling what they know. That doesn't rise to the legal definition of "torture", at least not in this neck of the woods.
Perhaps the terrorists should have chosen to attack some other country, one that forbids waterboarding. Since they know the U.S. is not such a country attacking us anyway is practically begging for a 'boarding.
Omar Khadr ... rights
Most of your misconceptions about Khadr's "rights" can be cleared up by understanding how our Supreme Court has dealt with conflicts between treaties and the Constitution. The Supreme Court cases Seery v. United States, Diggs v. Schultz, and Reid v. Covert establish the subordination of treaties, granted authority by the Constitution under Article VI, to the remainder of the Constitution.
Take this recent example: America is a signatory to the U.N. Charter. The U.N., under pressure from the Organization of the Islamic Conference, adopted a resolution censoring religious speech. In America that resolution is nullified by the First Amendment to our Constitution, which grants freedom of speech and religion. (We've also made explicit reservations to the Charter, but never mind that.) The President's powers of Commander in Chief are likewise granted by the Constitution; therefore U.N. resolutions presuming to constrain that authority are equally meaningless.
Right to a Canadian Trial:
Rendition may be privilege or punishment, but it is not a right. Unlawful combatants captured in war are under military authority, thus Article VI is preempted.
Right to a Civilian Trial, Right to a Speedy Trial:
Enemy belligerents have no such rights.
Recent decisions by the Supreme Court have raised issues of justice for enemy belligerents and due process for determining belligerent and lawful vs. unlawful combatant status, so there are many difficult issues which haven't been definitively sorted out just yet.
The last time "unlawful belligerent" status came up we were summarily executing inept Nazi saboteurs whose combatant status was unquestionably obvious. With terrorists it's a little more tricky, if for no other reason than it's not always obvious whether a particular person of interest is a terrorist. Not every crazy with a bomb is an unlawful combatant. But is every Islamic fundamentalist with a bomb? Who knows?
Geneva Convention:
Doesn't apply to unlawful combatants; re: summary execution of Nazi saboteurs during WWII. The expectation of Geneva Convention rights for unlawful combatants is a very recent concept.
What legal or humane rights does he have?
At minimum a military tribunal with representation.
The Supreme Court has taken more of an interest in the rights of belligerents and unlawful combatants than at any time in history, so everything is very subject to change.
I'm not sure why people think torture would work
Don't know about torture, but waterboarding works. It's just a question of perseverence. If we'd quit waterboarding Khalid Sheik Muhammad after 182 passes we'd have been quite frustrated indeed. Instead he gave us the names and home addresses of, among others, the [would-be] LA tower bombers -- after 5 sessions and 183 total 'boardings. Thus in waterboarding we find a lesson for life: if at first you don't succeed, try try again.
it gives more cannon fodder for our enemies to use against us
That's completely ridiculous given the ruthlessness of the Russians. Were we as ruthless as they or they as restrained as we would fewer children have died in Beslan or more have died on 9/11?
Our enemies are aiming for mass murder with maximum casualties. They were before we waterboarded them and they would be had we never waterboarded them. On the other hand, every terrorist network we roll is one less chance at another massacre.
Given our opponents' invariant desire to inflict maximum casualties the only way we can make things worse for ourselves is not if we waterboard but if we fail to.