Sport Pilot,
I think I read somewhere in all of the reports that this took place at the FS's home field. He lived there supposedly, and was returning from another airport. He probably therefore was "invited" to it, if he lived there or kept his plane at this airport.
I have attended some of thses loosely supervised, EAA type fly-ins like this before and if anyone wants to fly RC there, they are encouraged to do so by the FS pilots, but we are extremely careful, stay away from the runway and only fly with one or more spotters to keep an eye out for surprise traffic.