You keep using the LP as an example....but where's the evidence? In 2008, the LP sacrificed its "purity" and nominated Bob Barr. While I supported Barr at the time, I wish we had listened to the purists in that case. In 2012, the LP again rejected the "purist" alternative and nominated Gary Johnson. While I was often critical of Johnson, I think that it was a very wise choice.
Again, even the recent story of the LP indicates that "true believers" criticized by Hoffer were more losers than winners in getting their way.