Willis Carto has for almost a lifetime been among America’s most prominent promoters of antisemitic conspiracy theories and Holocaust denial (that’s not how he describes himself, but that’s another matter). He founded Liberty Lobby in 1955, and Institute for Historical Review (IHR) in 1979, as an organization dedicated to publicly challenging the "myth of the Holocaust." The IHR sought from the beginning to attempt to establish itself within the broad tradition of historical revisionism, by soliciting token supporters who were not from a neo-Nazi background such as James J. Martin and Samuel Edward Konkin III, and by promoting the writings of French socialist Paul Rassinier and American anti-war historian Harry Elmer Barnes to attempt to show that Holocaust denial had a broader base of support besides just neo-Nazis. The IHR brought most of Barnes' writings, which had been out of print since his death, back into print. However, most of IHR's supporters were neo-Nazis and anti-Semites, and while IHR included token articles on other topics and sold some token books by mainstream historians in its book catalog, the vast majority of material published and distributed by IHR was devoted to questioning the facts surrounding the Holocaust.
In 1984, Carto was also involved in starting the Populist Party, which was (not to be confused with the Populist Party of 1889 and) little more than an electoral vehicle for current and former Ku Klux Klan and Christian Identity members.
His wikipedia page is here. I am not going to link to his homepage or any homepage associated with his organizations.
To get a full picture of Carto’s insane conspiracy mongering, have a look at his earlier Liberty Lobby. Apart from standard conspiracy theories, such as New World Order related ones and John F. Kennedy assassination conspiracies, Carto and his gang has always been taken by the Bilderberg conspiracy, going so far as to send reporters every year to "infiltrate" the Bilderberg conferences and report on their nefarious activities.
This already sets the stage for crank magnetism, and Carto has been an ardent promoter of alternative health remedies, including colloidal silver, Laetrile, shark cartilage and chelation therapy. He is also a numerologist.
Perhaps most interesting in that respect is Carto’s involvement with Scientology. Back in the beginning, the Church of Scientology representatives viewed Carto's organizations as useful media for gaining popularity and respectability. Carto, with his critical view of "establishment" press (i.e. conspiracy theories), had reached quite a number of people, and scientologists flocked to the IHR and subscribed to Carto's publications. Many Scientologists, including the current International Public Affairs Officer Alex Jones, praised Carto and his magazine "The Spotlight" (the percurson to IHR) as "a defender of individual liberties." A scientologist was also the director of IHR (the scientology church has subsequently withdrawn its official support, notably after the tax exemption rules from 1993).
Despite his claims to the contrary, Carto and his group are ardent neo-Nazis (follow the link for recent activities).
Diagnosis: Vile and utterly delusional loon. Zealous. Is still extremely dangerous, despite the fact that his impact is probably limited to a relatively small group (his conspiracy theories seem to draw sympathetic attention, by crank magnetism, from other conspiracy theorists and whale.to readers, however).