Some people get a bit upset when you use the term "conspiracy theory", so I think it's good to be clear on what you mean. One might say "I know it when I see it", like say 9/11 no-plane theories, or fake moon-landing theories. I think Aaronovitch has something right here: Aaronovitch, David (2010-01-19). Voodoo Histories: The Role of the Conspiracy Theory in Shaping Modern History (pp. 5-6). Penguin Group. Kindle Edition.