Wikipedia has been accused of being biased against challengers to scientific orthodoxy due to efforts by editors having affinities with the Skeptics movement. Examination of Wikipedia, including entries on fluoridation, the origin of AIDS and vaccination, reveals several characteristics typical of a Skeptics sensibility, including the definition of scepticism, lists of deviant ideas, derogatory labelling of heterodox viewpoints, and categories established without reference to reliable sources.
…For topics, I picked three areas that I have studied in some depth: fluoridation, the origin of AIDS, and vaccination [e.g., Martin, 1991; Martin, 2010; Martin, 2018]. Having analysed the debates in these areas gives me a basis for assessing Wikipedia treatments. Wikipedia editors would probably say that, because of my studies, I am not in a position to provide a neutral assessment. That would be to apply Wikipedia rules. However, I am writing here as a social scientist, not as a Wikipedia editor, so standards and conventions common in social science apply, which means that demonstrated expertise is seen as an asset rather than a conflict of interest.
Water fluoridation controversy
Fluoridation refers to adding compounds containing the element fluorine to public water supplies. In solution, fluorine becomes its ionised form fluoride. The aim of fluoridation is to reduce the incidence of tooth decay in people, especially children, who drink the water. Fluoridation was first widely introduced in the United States in the 1950s and then was taken up by governments in a number of other countries.
From its earliest days, fluoridation was controversial. Proponents have argued that it greatly reduces tooth decay and has few if any adverse effects. Critics have claimed that fluoridation can lead to skeletal fluorosis, reductions in IQ and a number of other adverse effects. Critics have also questioned the scale of the benefits. The controversy also has ethical and political dimensions. Proponents say fluoridation is especially important for people unable to afford dental care, whereas critics say fluoridation is compulsory medical treatment with an uncontrolled dose. Proponents usually say decisions should be made by governments on advice from health experts whereas critics often support citizen participation, for example via referenda [Freeze and Lehr, 2009; Martin, 1991].
Wikipedia has an entry on water fluoridation, which addresses many matters such as evidence, mechanism, alternatives, history and economics. There is a separate entry titled “Water fluoridation controversy,” which discusses the antifluoridation movement. On 6–7 November 2016, this latter entry was added to the sidebar about “Alternative medicine” in its subcategory of “Conspiracy theories,” implying that antifluoridationism is a conspiracy theory.
In the history of the fluoridation controversy, there have been a few opponents who have alleged that certain groups have promoted fluoridation to serve their vested interests. However, based on my studies of the controversy [Martin, 1991], these views have always been marginal. Most antifluoridation campaigners are driven by concerns about adverse health effects and the imposition of a semi-compulsory treatment at an uncontrolled dose.
Wikipedia’s entry on the water fluoridation controversy contains some discussion of conspiracy theories, but no comment about whether these views are prevalent or important among antifluoridation campaigners and supporters. Furthermore, there is no attempt to say that antifluoridationism is itself a conspiracy theory. The point here is that the conspiracy-theory tag has been applied by some editors of the Alternative Medicine sidebar without sufficient justification in the relevant entry.
Interestingly, the mainstream history of promotion of fluoridation can be read as a conspiracy by a number of Wisconsin dentists who campaigned in the face of official resistance to adding fluoride to public water supplies [McNeil, 1957]. In the early years, support for fluoridation challenged mainstream views, but because the conspiracy-theory label is only applied to current heterodoxy, profluoridationism has never been described as a conspiracy theory — at least not in Wikipedia.
The Encyclopædia Britannica  has some information about fluoridation. It is one-sided, entirely supportive of fluoridation, but has no mention of conspiracy theories.
In summary, on three topics covered by Wikipedia — fluoridation, the origin of AIDS and vaccination — critics of scientific and medical orthodoxy have been labelled conspiracy theorists. In each case, this label seems more stigmatising than descriptive, given the lack of justification for the label in the relevant entries. The Encyclopædia Britannica does not associate any of these topics with conspiracy theories. Compared with Britannica, Wikipedia editors seem to have gone to a lot of trouble to identify and discredit so-called fringe beliefs in science and medicine. In this treatment, the outcome of Wikipedia editing seems to be aligned with the agenda of the Skeptics movement.
*Original full-text study online at https://jcom.sissa.it/archive/20/02/JCOM_2002_2021_A09
*Also available in PDF