This is evidently true even of credentialed experts. Few Doctors have ever read the scientific literature pertinent to vaccines, for example, so they are as subject to group think and interest group capture as anyone else. In the words of Le Bon, they are a "Caste".
“The medical profession is being bought by the pharmaceutical industry, not only in terms of the practice of medicine, but also in terms of teaching and research. The academic institutions of this country are allowing themselves to be the paid agents of the pharmaceutical industry. I think it’s disgraceful.” – Arnold Seymour Relman (1923-2014), Harvard Professor of Medicine and Former Editor-in-Chief of the New England Medical Journal http://www.commercialalert.org/relmanangell.pdf http://www.ncbi.nlm.nih.gov/pubmed/12561803
Only at most 40% of medical practice is supported by science according to all the surveys of which I'm aware cf the following:
John S Garrow BMJ. 2007 Nov 10; 335(7627): 951.doi:10.1136/bmj.39388.393970.1F PMCID: PMC2071976 What to do about CAM?: How much of orthodox medicine is evidence based? http://www.dcscience.net/garrow-evidence-bmj.pdf
http://www.fas.org/ota/reports/7805.pdf Assessing the Efficacy and Safety of Medical Technologies, Office of Technology Assessment, Congress of the United States (1978)
http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=101041 Jeannette Ezzo, Barker Bausell, Daniel E. Moerman, Brian Berman and Victoria Hadhazy (2001). REVIEWING THE REVIEWS . International Journal of Technology Assessment in Health Care, 17, pp 457-466.
http://clinicalevidence.bmj.com/x/index.html BMJ Clinical Evidence
http://www.huffingtonpost.com/dr-larry-dossey/the-mythology-of-science_b_412475.html Larry Dossey, Deepak Chopra, Rustum Roy, The Mythology Of Science-Based Medicine
S. A. Greenberg, "How citation distortions create unfounded authority: analysis of a citation network", BMJ 2009;339:b2680 http://www.bmj.com/content/339/bmj.b2680