Mark Hoofnagle at Denialism Blog hits the hail on the head:
In fact, if there is a unifying theme of denialism, it is that any extreme of ideological thinking leads to the necessary denial of fact. When one considers the causes of denialist worldviews, one sees again and again some form of fundamentalist belief. Fundamentalist religion leads to the rejection of evolution. Free-market fundamentalists are the leading source of anti-global warming denialism. On the liberal side, a mixture of technophobia and neo-luddism leads to paranoid suspicions about everything from GM crops causing non-existent illnesses to fear of harmless radio technology such as wifi to the fear of vaccines and medicine innovations exemplified by the HuffPo cranks and the evidence-based medicine/HIV/AIDS denialists like Mike Adams and Gary Null.
Any dogma that gets any followers is likely to be (a) simple and (b) emotionality satisfying, at least to some people. In fact any belief system must be simpler than reality, since reality is vast and probably not fully comprehensible to the human mind anyway. Once people become adherents of a dogma, they are likely to hold tight to it, since it’s their intellectual comfort blanket. And when reality proves that their dogma is at least partly wrong — as all dogmas must be, even though they are probably partly right, too — then the adherent is drawn into conflict with reality, and resolves that conflict by simply pretending that the uncomfortable truth isn’t there. And then the more serious of the adherents erect whole intellectual edifices, founded on bullshit and wish-fulfillment fantasy, as to why reality isn’t real.
What’s the cure for this? Simply to realise that any simple, pat, belief system isn’t going to be the whole truth, even if it does have good points. Put simply, no belief system about how the human world works is entirely correct, or is any widely-held belief system likely to be entirely nonsense. For example:
Religion: God may not exist, but nevertheless it is still bad for people to murder or steal from each other.
Free markets: are an efficient way of allocating scarce resources, under many circumstances, but they are not the solution to all human-organisation problems.
Medicine: some medicines have genuinely harmed patients, but most do good, and by spreading panic about vaccines etc one is almost certainly doing more harm than good.
Technology: most technology leads to humans living longer, more fulfilled lives; but some technologies have lead to a diminution of human happiness (e.g. telemarketers and spammers)