The New Scientist has a special report on the roots and methods of denialism. Should be useful reading for anyone who ever finds themselves talking to creationists/climate change deniers/9/11 Truthers/anti vaccination types/that bloke in teh pub who knows what really happened to Elvis.

How to be a denialist

Martin McKee, an epidemiologist at the London School of Hygiene and Tropical Medicine who also studies denial, has identified six tactics that all denialist movements use. “I’m not suggesting there is a manual somewhere, but one can see these elements, to varying degrees, in many settings,” he says (The European Journal of Public Health, vol 19, p 2).

1. Allege that there’s a conspiracy. Claim that scientific consensus has arisen through collusion rather than the accumulation of evidence.

2. Use fake experts to support your story. “Denial always starts with a cadre of pseudo-experts with some credentials that create a facade of credibility,” says Seth Kalichman of the University of Connecticut.

3. Cherry-pick the evidence: trumpet whatever appears to support your case and ignore or rubbish the rest. Carry on trotting out supportive evidence even after it has been discredited.

4. Create impossible standards for your opponents. Claim that the existing evidence is not good enough and demand more. If your opponent comes up with evidence you have demanded, move the goalposts.

5. Use logical fallacies. Hitler opposed smoking, so anti-smoking measures are Nazi. Deliberately misrepresent the scientific consensus and then knock down your straw man.

6. Manufacture doubt. Falsely portray scientists as so divided that basing policy on their advice would be premature. Insist “both sides” must be heard and cry censorship when “dissenting” arguments or experts are rejected.