Rush has not said that. I would like to see transcripts of where he stated such. Rush's main thrust is to question those who are "certain" that GW is man-made; that it is "settled science." Rush like many, myself included, who are utterly exasperated at the insanity of those who believe the Earth's climate is at the "tipping point." I am an engineer who has been involved in circuit and systems modeling. Just dealing with how to determine valid initial conditions is difficult enough; handling non-linearities is another layer of complexity.
My intuition would tell me that any output from models of the Earth's climate should be not taken as "truth or settled science." Who knows what seemingly "simple" parameters yet to be accounted for in their models, will result in vastly different results. The Scientist on Rush's show yesterday was a breath of fresh air over this non-problem. I was astounded when he said that precipitation is not an integral part of many models. That alone should give anyone pause over the claim of the nuts like Gore. I choose to be happy and appreciate the beauty of nature, knowing man will NOT destroy the climate. I fear the freaks on the left who have found yet another pathway to try impose their totalitarian hell upon civilization.
If Rush did say "Not our fault, therefore no global warming," it was more than likely said tongue in cheek and in order to illustrate a point. He likes to illustrate absurdity by being absurd.