If you actually read the cases summaries of the cases cited you can gain a greater insight. One was a pilot who flew some people while she was on a "training flight" and then accepted a considerable gratuity for doing so. Another was a flower cooperative in San Francisco (where else?) that was trying to get around the rules for commercial pilots by claiming they were not actually under hire since they were only flying the product of the members of the cooperative.

I can see no way that these cases can be construed into saying that some guy flying a noon time demo of a hobby RC plane is involved in a "business purpose." That is of course up to the FAA to determine, but simply saying that what you posted was what an attorney said is really kind of meaningless with regard to our situation.