It's unfortunate that he continued to draw attention to you. I'm sure that it took away from what he was supposed to be doing (teaching). I give you kudos for holding your ground and educating him while refusing to disarm. Perhaps he learned a lesson when no one else got riled up. Were you able to give him any OC pamphlets or something similar? It might not hurt to fire off a friendly email to IDGF asking that their volunteers be briefed on firearms carry. You could even go so far as to provide the briefing material. I guess the most important question is, did you pass the class?