I've been fascinated with the thought processes behind conspiracy theories for a long time. The Internet has made it much easier for these weird memes to survive and spread, and also for their propagators to portray themselves as engaging in impartial inquiry instead of irresponsible speculation.
Robert's Mozart conspiracy shares many traits with better-known conspiracy theories, such as creationism, Holocaust denial, and the 9/11 inside-job conspiracy. It's constructed out of the "anomalies" in the official theory, instead of deriving from independent lines of research. It depends on speculation about the usual shadowy cabals (the Freemasons, for instance) which can never, by definition, be verified. It handwaves away the work of the vast majority of musicologists and historians, and concentrates on one or two whose work is assumed to be reliable only because it seems to support what the conspiracy theorist already believes. And it dismisses all opposition to the theory as blind acceptance of the "paradigm." In truth, we accept the conventional scenario because it's supported by a mountain of data from independent lines of inquiry.
I noticed with amusement that certain MIMF members (particularly the Oceania contingent) were quite receptive to Robert's bizarre lucubrations. It just goes to show how unfamiliar people are with the tactics of conspiracy theorists, and how they pander to the cognitive biases of even intelligent people.