Arguing Against Scientific Consensus
Author's Note: This is an expanded version of this comment I wrote, with reference to this comment, by a regular commenter and apologist for various forms of purported therapeutic products and services which might more accurately be described (at least in this author's opinion) as "rank quackery".
In politically-controversial (if not scientifically-controversial) bodies of knowledge with large, well-settled factual support, it is a common occurrence to encounter those arguing against those bodies of knowledge, specifically by attacking what would otherwise be the entirely unsurprising near-unanimity - or, as used in the rest of this post (and elsewhere), the consensus - among relevant subject-matter experts.
There are two rhetorical devices that can be used to mount such attacks. The first, which I shall not examine in detail here, is the technique of asserting the existence of a countervailing bloc of subject matter experts, a bloc which is asserted or insinuated to be of some significance as compared to the subject matter experts upholding more mainstream positions. Such is the technique used by the OISM Petition Project (discussed here and here at the climate science website Skeptical Science) with respect to global warming/climate science, or by, say, various forms of creationists with respect to biological evolution of organisms.
The second rhetorical device, which is the subject of this post, is to attack the very notion of scientific consensus among subject-matter experts. Perhaps the most famous such line of argument was made by the late physician, author, and film/TV producer Michael Crichton: