There are some equally irrational, sincerely held, if not more ridiculous, beliefs out there:

Flat earth society: http://www.theflatearthsociety.org/cms/

James H. Fetzer's entire career after 1990: https://en.wikipedia.org/wiki/James_H._Fetzer

Should I continue with links? Because that last one really bums me out beyond belief. Fetzer seriously seems like a body that inherited the respect of an intellectual but deteriorated under the stress of an undiagnosed paranoid psychosis.