Here's what Amanda has to say about that:
This is a complete disaster. For reasons I can't quite understand, Jenny McCarthy is dedicated to fighting medical science on multiple fronts on the theory that she, as a celebrity who has given birth, understands way more about disease and biology than mere doctors and scientists, with their facts and their evidence.
Amanda noticed an awful lot of magical thinking about food on McCarthy's blog, but what she (rightly) focuses on is the irresponsibility of giving an anti-vaccination activist such a powerful public voice. (With her two mega-selling books, McCarthy has already given her idea that vaccines caused her son's autism way more of a public hearing than it should have).
Anti-vaccination ideas have become more and more widely accepted in America, with the result that vaccine-preventable diseases have started to reappear in some communities.
(Thank you to Bev of Asperger Square 8 for this image, and for the one at the top of the page).
While I'm pretty sure I haven't yet teased out all the different cultural and political strands making up the anti-vaccination (or anti-science in general) snarl, I do have a few starting points. I think part of it has to do with the way most human minds work.
People don't deal with randomness well. One of the things our brains do really, really well is detecting patterns, so it's not surprising that we've learned to play to this strength and see patterns everywhere. The other thing we do really well is express very specific ideas about --- as Steven Pinker says in his book The Language Instinct --- "who did what to whom". Because we've developed language, we can put events in order and indicate cause and effect. I think these built-in biases make us a lot likelier to see 1:1 cause-and-effect relationships, even where none really exist.
Another inherent bias we seem to have is what Daniel Dennett calls an "agent detector." When most people perceive motion, they evaluate whether that motion is likelier to come from a living or nonliving source. Dennett hypothesizes that, throughout much of our evolutionary history, it was advantageous for humans to be able to deduce, without needing to see the beast itself, when there might be a dangerous animal (or hostile group of humans!) in the vicinity. Accordingly, we're wired to err on the side of caution, and impute unexplained sounds, movement etc. to unseen living beings.
What does that mean for Jenny McCarthy? Well, I think it's making the impersonal, luck-of-the-draw genetic explanation for autism ring false to her --- she wants something more concrete, something she can fight against. It's probably easier for her to visualize evil little mercury atoms glomming onto her little boy's brain cells than it is to visualize his DNA simply encoding proteins that work together to build a slightly different nervous system than hers. Plus, with the evil-little-mercury-atoms option, she can conceive of her son's autism being a separate entity from her son, which she cannot do if her son simply developed differently.
It also gives her an illusion of control --- if Evan (her son) was born with different genes that led his embryonic nervous system to develop differently, there's nothing she can do to change that. If, however, she can simply rid his body of the thing she's convinced is in there, making him different --- well, she will! No power in the 'verse will stop her.
(That's another interesting fallacy of the autism-is-mercury-poisoning brigade: if they're right, the "damage" is irreversible. Mercury kills brain cells, and brain cells don't regenerate. You chelate someone who's been mercury poisoned to stop the cell-death process: you're cutting your losses, not restoring what's already gone).
Anyway, the "illusion of control" thing is very much up Oprah's alley, considering her past endorsement of The Secret, which told millions of gullible readers that all they need do is concentrate really hard on what they want from life, and "the universe" (ooh, hey, another vaguely anthropomorphic entity!) will reward them with it.
I've listed the individual psychological and cognitive factors that I think contribute to the surprising prevalence of magical thinking in a technocratic society above, and while I certainly think there's also a slew of societal, cultural and historical factors involved, I don't want to list them all here.
(NB: I don't recommend reading very many of the comments at Pandagon; while the commenters there are generally intelligent, reasonable and scientifically literate --- as opposed to commenters at most major news websites! --- they almost all share the anti-vax crowd's assumption that autism is a terrible, horrible thing that ought to be eliminated as soon as possible. And reading comment after comment to that effect can be pretty demoralizing).