At the end of his big bestseller Influence, he goes into a long-winded moralization about how he hopes his work helps people resist the terrible influence of immoral salesmanship... for example by being mindful of the "secret weapons" of Social Proof and Authority and Scarcity.
of course, he writes this in a book (a NATIONAL BESTSELLER as it says on the cover) that is literally covered in testimonials and promotional blurbs from "thought leaders" with credentials, mainstream publications like HBR and Fortune, praising Cialdini, PHD for revealing "little known secrets of Master Influencers" yada yada yada.
Good catch. I did not notice he had written the article.
Well sure, buying the book may show he's a reliable source of information on persuasion.
But, you know, being a very widely cited researcher may show it better. :-) I've encountered references to his work in many places.