Wikipedia is an on-line encyclopedia founded in January 2001. Its content is created by anyone who chooses to contribute. Inviting anyone to contribute poses unique challenges for establishing guidelines. Wikipedia offers several benefits: high availability of diverse information, access to free material, encouragement of careful citation, community of collaborative work... Wikipedia has sometimes been criticized for the integrity of its information. However, even that can be viewed as a positive if it offers readers exercise in reading with a critical eye.
The potential audience is much broader. Nobody owns contributed content. The standard for inclusion is verifiability, not truth. Full rigor is not feasible in an encyclopaedic setting. Wikipedia is not like a textbook. (Other core policies that I have failed to mention.) Any argument presented should be supported by a source. The (expert) knowledge of the editors, although very helpful in writing, cannot be the basis for inclusion or exclusion of material.
(If it makes sense for the tone of the journal, a few vignettes might be appropriate in order to illustrate why we follow our guidelines. Vignettes could include crackpots, amateurs with unverified mistaken work, geniuses who have unverified correct work, and a person with an unorthodox original approach.)
In this context it may be useful to advise new editors against editing articles about oneself, one's institute and direct colleagues, and one's own work. It is much easier the learn the ways of WP editing articles some safe distance from one's own interests.