I guess I am a little different. I usually take my stuff out then ask. That way they can see that I am either an idiot or knowledgeable.
After doing this with my 1/4 scale Giles, I have had people ask me if I knew how to fly it. I tell them a little and they want me to prove it. How do you prove you can fly unless you fly. I just show them the wear and tear on the plane and said it is due to friction.
At one field, the guy got really really mad but stood out at the box with me until I did a stall turn and transitioned into an inverted low speed pass. He turned around and sat down.
I know it is bad but I loved doing that.