Be done with this negative interaction. You don't need more conflict in your life. Either tell him to pound sand, or tell him you'll turn it over to an FFL in your state and he can deal with it from there. This is simply not worth the emotional investment it's getting.
This "advice" keeps popping up. I doubt that any FFL would want to get involved. I don't believe they'd be legally obligated to get in the middle of a cluster [bleep].
