So, how/when do you think the legend of the FMA ban began?
To be honest, based on the evidence, I think it began with a misinterpretation of the section "Maikling Kasaysayan ng Arnis " (A short history of Arnis)that Buenaventura Mirafuente wrote in the book "Mga Karunungan sa Larong Arnis" (Lessons in the Sport of Arnis) that was edited by Placido Yambao. Mirafuente wrote that:
At nang ipagbawal ni Don Simon de Anda y Slazar, nuong 1764, ang anumang uri ng laro..
"Laro" can be translated as "sport" or "play". So this would be translated as "a ban on any form of sport", not necessarily a ban on martial arts training.
However, people who would want to liken the ban to the edict issued by the Satsuma Clan banning weapons on Okinawa (another historical controversy), would probably want to interpret it as a martial arts ban.
Just my 2 centavos worth.