Second: the CIA's role in the Iraq is complicated, and apparently significant numbers of senior people inside CIA were opposed to the case made for Hussein's weapons programs. Most of what I've read suggests that DoD and the VP's office was the primary driver for the war and for the perspective on intelligence supporting it. A good book here is Gellman's _Angler_.
Third: "the CIA" isn't a single monolithic thing and, in particular, the leadership at CIA changes dramatically across administrations --- as, in fact, it did within the Bush administration (similarly: Bush's first-term DoD leadership bears little resemblance to Robert Gates's DoD).
Fourth: the argument you're making is an essentialist one --- suggesting as it does that if CIA was ever wrong about anything, then that is dispositive evidence that the CIA is always wrong. But that's an absurd rhetorical position to take. If it's the case that CIA is uniformly (or, perhaps, in some Byzantine fashion) wrong, you have to support that claim with more evidence.