"So the question, then, is for conservatives: on what major policies is the bulk of the Democratic Party establishment ignoring — or, Norquist-like, promising to ignore — the evidence? And if that behavior isn't as prevalent among Democrats, why is that?"
This is a balanced and thoughtful piece from (that mentions Professor Krugman) on why facts have such a liberal bias. Of course the facts do not have any bias, it is the people "interpreting" or willfully ignoring the facts.
To answer Ezra's question, is there a liberal equivalent of climate denial, the answer is clearly no.
To forestall some needless debate, let me mention (and you can go Google and check) that vaccine denial and GMO paranoia are equally prevalent among conservatives and liberals.
There is without a doubt a very very strong anti-Science faction in the republican party who hates and fears Science, Technology, and Progress.
Long story short, conservatives value authority, in-group loyalty, and purity of ideology way more than liberals. The result is that the conservatives form a bloc, the liberals a coalition.
This means that if a portion of the conservative party has a big problem with some facet of reality (evolution for the Christians, climate change for the CEOs; or, one for the fundies and the other for the funders), and if the other group doesn't really care, then they'll both accept it, fold it in, and, boom, suddenly you have fundies trying to rationalize why God would never allow climate change while the Koch brothers pay for the Discovery Institute's legal battles.
But in the liberal party, we aren't willing to throw ourselves under the bus to support an ally's asinine beliefs. You have a problem with something? That sounds like your problem to me.
To put it another way. The liberal coalition might fail to do the right thing, but the conservative bloc can always accomplish the wrong thing.