I agree that the attacks on Bain soured Rush on both Newt and Perry. He felt that was an affront to capitalism and capitalism is probably as close to his heart as any other issue.
I think Rush was more forgiving of Perry and his attacks on “vulture capitalism” because Perry started out as a candidate that Rush felt he could support. As far as Newt was concerned, he had to earn Rush’s good will from the get-go. Rush was disinclined to be forgiving about the couch time with Pelosi. Particularly after the Juan Williams debate, Rush was in the early stages of thinking he might trust Newt again. Then Newt started the Bain bashing (which Perry subsequently joined in on). IMO, when both candidates knocked that off, in Rush’s eyes it might be forgiven in Perry’s instance, but not in Newt’s. I could be completely wrong about all of this, but I don’t think so.
IMHO, Rush really started watching Newt with a wary eye a few years back when Newt declared, "the era of Reagan is over." Rush blasted Newt on air to the point that Newt requested to come on Rush's show and clarify his remarks. IIRC, this was around 2008 or 2009.
Rush, as a communications professional, though it was a poor choice of words even if well intended, and he was right.