One of the things that strikes me about the commenters actively opposing vaccinations – e.g. on the many news stories about NZ’s measles outbreak – is their continued readiness to state and repeat mistruths and inaccuracies. You see it all the time, & I have to wonder – is there just this underlying assumption that no-one will actually check?
Yes, I’d say that assumption definitely exists – it was easy to find evidence that the claim that some states have removed medical exemptions is incorrect, but how many would actually fact-check it?
And combine that with the fact that it’s actually really hard to keep up with the sheer number of claims like this: they crop up virtually unchanged on just about every measles-related media post I’ve seen. In this, infectious-disease proponents are working from the same play-book as creationists: the Gish Gallop** is a technique for preventing opponents from rebutting their claims – & also for giving the impression that the Galloper has a large amount of evidence in support of their position. It works particularly well in the ‘free-form’ format of a Facebook thread, where comments can be hard to track & where the audience may not have a good knowledge of the subject.
Here, from Rational Wiki, is the reason why it’s a problem (in more ways than one):
The Gish Gallop is often used as an indirect argument from authority — as it appears to paint the Galloper as an expert in a broad range of subjects (in which case it may take several actual experts in multiple fields to properly debunk the Gallop) or with an extensive knowledge of an individual one. Simultaneously it presents opponents (in spoken debates) or refuters (in written, Internet-based ones) as incompetent bumblers who didn’t do their homework before the debate. Such emphasis on style over substance is the reason many scientists disdain public debates as a forum for disseminating opinions.
** The Gish Gallop is named for the creationist Duane Gish, who was a master of the technique.