You're right of course - having policy niggles or disagreement is not a good sign of irrationality. But the harder the science gets, the more disagreement becomes irrational. And I've seen people cycle through "global warming isn't happening" to "it's happening but it's natural" to "it's man-made but it'll be too expensive to do anything about it" in the course of a single conversation, without seeming to realise the contradications (I've seen theists do the same, but this was worse).

So yes, mild anti-AGW (or anti-certain AGW policy ideas) is not a strong sign of irrationality, but I'd argue that neither is mild theism.