This is a fairly long post, so quick summary: the MMR-autism link is bogus; the uncertainty that the MMR-autism claim has created has led to concrete harms in terms of public health; and the widespread acceptance of the claim is typical of modern skepticism about the “scientific establishment.”
I use the MMR-autism issue in a talk I have given to scientific groups about science journalism and the issues that arise at the intersection of science and public policy controversies, one of a number of examples wherein people with strongly held views on a topic find scientific outliers to support their view, shrugging off a widely held mainstream consensus. No particular side of the traditional liberal-conservative spectrum is immune to this – the right does it on climate change, and the left does it on GM foods. Our Universal Acid author suggests that a strong thread of anti-intellectualism afoot today is one explanation:
It doesn’t do any good to report that “the overwhelming majority of experts have concluded there is no link between the MMR vaccine and autism,” because scientific “expertise” (and science itself) has lost at least some of the patina of authority it once commanded. The anti-vaccine movement is thus intimately connected (as an intellectual and social phenomenon) to quack medicine, conspiracy theories, and even (loosely) creationism.