How about this:
"Am I being detained?"
-- Man with a gun call
"Were there any laws broken?"
-- We don't know (the law)
"Did the caller say this person was waving the gun or was it holstered?"
-- In the holster
"Great, so no crime committed, am I free to go then?"
-- Because we're investigating
"When did you guys start investigating lawful activities?"
"You just said there was no crime, can I please leave now"
-- We're investigating
"What though, you just said there was no crime"
-- you could be a felon, we don't know
"so could anyone else"
We don't know if you're crazy
"anyone unknown to you could be crazy"
-- The public doesn't know this is legal
"perhaps you could educate them about their right to open carry so that they too can protect themselves?"
"OK, we'll you officers seem like professionals so I'll hang out for a while and help educate you on the various laws that it looks like your superiors have failed to make you aware of. I am not being detained though since you have no reason for a Terry stop, so I won't be consenting to any searches nor providing you with any information other than the various laws that you'll be needing today, which by the way are right here if you'd like to read about them."