It's about the pathologizing of opinions you don't agree with. Mind you, I have no problem with ending an exasperating disputation with "You're nuts. I can't discuss this with you."
But that's not a diagnosis. While I am fully aware of group and mass psychological themes, I only confer a diagnosis on those who pay me to do so. Even then, I often cannot give them a label because every person is unique.
I have more science under my belt than 95% of the folks I encounter who dispute my skepticism about AGW. But, in the world of science, the only proper attitude towards anything is skepticism. That's how it works. "Proof" is usually very elusive. We have many theories, few truths, and no Truths.
Brendan O'Neill at Spiked reports on the disease of Anthropogenic Global Warming Denial. One quote:
This weekend, the University of West England is hosting a major conference on climate change denial. Strikingly, it’s being organised by the university’s Centre for Psycho-Social Studies. It will be a gathering of those from the top of society – ‘psychotherapists, social researchers, climate change activists, eco-psychologists’ – who will analyse those at the bottom of society, as if we were so many flitting, irrational amoeba under an eco-microscope. The organisers say the conference will explore how ‘denial’ is a product of both ‘addiction and consumption’ and is the ‘consequence of living in a perverse culture which encourages collusion, complacency and irresponsibility’ (1). It is a testament to the dumbed-down, debate-phobic nature of the modern academy that a conference is being held not to explore ideas – to interrogate, analyse and fight over them – but to tag them as perverse.
"Eco-psychologists"? May I conjecture that these people are nuts?