It really shouldn't be necessary to even discuss the conspiracy theory, but let's summarize some salient facts. First, the US had had an official policy since fall 1998 of regime change in Iraq. Second, Saddam Hussein had a record of invading neighbors without provocation and had used weapons of mass destruction in war and against innocent civilians. Third, Saddam Hussein had know-how and infrastructure to support the production of nuclear, biological and chemical weapons. Fourth, Saddam Hussein had ordered international inspectors out of Iraq with known stockpiles of chemical weapons, and there was no incentive (given the economic sanctions would stay in place) to stop him from relocating and/or replenishing or expanding stockpiles. Fifth, Iraq had materially violated ceasefire conditions ending the first Gulf War and had violated some 17 UN resolutions. Sixth, multiple international intelligence agencies had corroborated WMD-relevant findings, some of which we now know were erroneous. I should point out that the international inspectors just before liberation were convinced the Iraqis had WMD's and in fact found things like pamphlets on how to hide things from inspectors, Iraqi troops and hospitals had been issued antidote supplies, there were accounts of usable missiles buried intact underground, with many missiles exceeding the maximum range limit. Saddam Hussein also had given some provocative interviews when he said his biggest regret during the first Gulf War was not having a nuclear weapon to ward off the international coalition. And needless to say, Saddam Hussein had motive to strike back at the US, at least some operatives in the US whom were arrested post 9/11--and in fact attempted to assassinate former President G.H.W. Bush over his trip to Kuwait during the Clinton Presidency.
The indisputable fact is that whatever the nature of the evidence was, many Democratic senators were convinced of the Hussein threat based on the same intelligence Bush had access to and voted to authorize use of force, and initial support for the liberation of Iraq had 75% approval in some polls. The buyer's remorse we see in the years following the invasion had more to do with bad post-liberation mistakes and mismanagement (e.g., disbanding the Iraqi army, inadequate manpower to stabilize the country and the wrong strategy (i.e., conventional versus counter-insurgent tactics)) than disillusionment with the initial case for liberation, which is the focus of this conspiracy allegation. We should also remember the context of the aftermath of 9/11; we saw less than 2 dozen terrorists, in addition to the unconscionable loss of life, had caused hundreds of billions of dollars of damages to the economy in terms of damages to airlines, insurance companies, and other elements reducing the GNP. Especially worrisome was the concern that anti-American rogue nations with WMD know-how and economic resources (such as Iraq's oil revenues) could provide training, weapons or resources to terrorists. I suspect Bush, determined that a second attack would not happen on his watch, perhaps leaned to a strategy of "act now, apologize later".
This conspiracy theory that the Angry Left suggests the real intent of waterboarding was to prove an Iraq link with Al Qaeda is absurd. The Bush Administration never claimed that Iraq was responsible for 9/11. It went after the Taliban government which was protecting Al Qaeda and Osama bin Laden. It went to the United Nations to make its case against Iraq, something it would not do if it felt there was a connection.
I will agree that the American public felt there was a link between Iraq and Al Qaeda, but this was not based on the claims of Bush and Cheney. I think that Bush and Cheney played up the contacts between Al Qaeda and Iraq and noted that Hussein had provided certain amount financing or training to terrorists (e.g., survivor benefits for Palestinian suicide bombers). I think many Americans at the time read something into the general, ambiguous statements made by the Administration based on a primary association between Al Qaeda and terrorism. I myself never personally believed there was a functional link between Hussein and Al Qaeda.
The fact is that Saddam Hussein and Osama bin Laden had different, conflicting agendas. Hussein was motivated by power, an ambition of expanding his rule across the Middle East; bin Laden is intrinsically motivated by religious fanaticism. I don't think either man trusted or was willing to be subjugated to the other. In fact, there was a natural alliance between the religiously purist Taliban regime in Afghanistan and Al Qaeda.
The conspiracy theory implies that the CIA interrogations were motivated by a political agenda and unconscionably questions the integrity and professionalism of CIA personnel. In fact, the CIA never suggested that the contacts between Iraq and Al Qaeda amounted to a formal relationship during the 1990's, and the 9/11 Commission and Senate Intelligence Committee findings, which took into account any findings that emerged during the period of the interrogations, do not indicate any new information on the nature of the relationship.
The implied criticism that the CIA had changed its orientation from gathering intelligence to coercing false confessions is unfair, unsupported by the evidence and is inconsistent with the fact that the use of enhanced techniques decreased with the time value of the detainees' knowledge of operations. This characterization of the interrogations also is inconsistent with the CIA's claims that maybe one-quarter of the human intelligence it got on Al Qaeda operations came from these interrogations--and reports that initial responses from detainess (in standard interrogation procedures) were of the nature, "Wait and see what's going to happen."
Finally, conspiracy theories generally collapse under conventional application of the principle of Ockham's razor.
