Today's Oakland [California] Tribune has a story from the Palm Beach [Florida] Post carrying the headline, "Sandy Hook truther fired by college." The story is evidently quite similar to one that appears in the New York Post under the title "Florida university fires Sandy Hook truther professor." As these two headlines indicate, the term truther is sometimes used as a stand-alone noun and sometimes as a modifier.
A Wikipedia disambiguation page asserts that truther may refer specifically to "people who thought the event [the Sandy Hook Elementary School massacre of December 14, 2012] was a false flag government attack"; to members of the "9/11 Truth movement"; to a book published in 2011 by Jonathan Kay titled Among the Truthers: A Journey Through America's Growing Conspiracist Underground; or to conspiracy theorists generally.
Leslie Savan, "From Simple Noun to Handy Partisan Put-Down" (New York Times Magazine, November 18, 2009) provides an excellent brief discussion of truther as part of a pejoratively intended -er family of names that opponents have assigned to conspiracy theorists/fringe political group enthusiasts—a word family that may include birther, [John] Bircher, grassy-knoller, mooner, flat-earther, deather, tenther, and teabagger. But aside from suggesting that truther may have been coined in late 2004 by 9/11 Truth movement member Jon Gold (based on a comment that Savan says Gold "wrote on his blog recently"), she doesn't inquire too deeply into the precise origin of the term or into its application to other groups and individuals.
Where and under what circumstances did the term truther originate?
When (if at all) did truther begin to be applied not just narrowly to 9/11 conspiracy theorists and Sandy Hook conspiracy theorists but to conspiracy theorists of any stripe?