We’ll restrict ourselves to giving honorable mention to Randy Stimpson for his rank crankery based on lack of expertise in the scientific disciplines on which he has plenty of intuitions that he’s not afraid to assert.
A more interesting form of conspiracy-driven pseudoscientific stance is taken in Robert Stinnett’s Day of Deceit. Given the prevalence and popularity of 9/11 conspiracy theories, you just knew that Stinnett’s particular conspiracy theory had to exist, didn’t you? Indeed, the particular conspiracy was alive and well before Stinnett decided to take it up. Now, Stinnett, who was a Naval photographer during WWII and is currently a fellow at the Independent Institute in Oakland, California, hasn’t, as far as we know, said anything about 9/11. His schtick is Pearl Harbor. According to Stinnett, the FDR government was well aware of Japan’s plans to attack Pearl Harbor before it happened and willingly went along with it to provoke a war. The conspiracy theory is aptly summed up here, laid out in some detail here; there is a good resource here (and perhaps here), and a comprehensive response to Stinnett’s assertions here; for some further debunkings of some of Stinnett’s particular claims, see this, and this. It is bunk.
Do you think Stinnett has changed his position in the face of all the evidence showing that he was wrong? Despite what Stinnett tries to argue, this is not a matter on which the jury of historians are still “out”. And yes, the theory is just as silly as 9/11 conspiracy theories. Gore Vidal seems to have been a fan, but Gore Vidal seems to have liked himself some conspiracy theories on occasion (including 9/11) and would certainly have merited inclusion in our Encyclopedia himself had he not gone off and died.
His Independent Institute, by the way, is a wingnut, global warming denialist think tank famous for pushing, in addition to Stinnett, the crankery of Thomas DiLorenzo.
Diagnosis: Old, cranky conspiracy theorist and pseudohistorian. Not entirely harmless, and the kind of crank that makes real historians have to deal with loads and loads of bullshit instead of devoting themselves to doing real work.