To argue that torture didn't work is to argue that efficacy matters. It doesn't. Torture is an international crime. It is immoral. It is a violation of the UN Convention Against Torture, the UN Universal Declaration of Human Rights, the Third and Fourth Geneva Conventions, and International law. Torture is a fundamental and without exception violation of human rights.
An argument that torture did or did not produce some useful information in a specific case legitimizes the argument that circumstance and/or results matter. They don't. Torture is immoral and illegal every time, regardless of torturer, victim, circumstance, or outcome.
Let us be perfectly clear on this: The question of whether or not water-boarding was of some value in the hunt for Bin Laden is irrelevant. Period. There can be no justification for torture.