Delphinium might correct some of the finer points of this, but I think a lot of that reputation about Idahoans being Nazis and white supremacists began when Mark Fuhrman bought a place up in Sandpoint during (or maybe it was after) the OJ trial.
I also remember the MSM and others passing off the whole Ruby Ridge scandal as “oh, that Randy Weaver was a white supremacist”. But you never see that sort of thing anywhere south of Post Falls.
(No offense to the Northern Idahoans on the Ping list or that have posted in this thread. :) ).