So correct me if I am wrong... But lifting up your shirt to point out your weapon to someone in public could be construed as brandishing? Or at least an act that could cause someone to become alarmed with in the sense of the law?
Next time just tell him to go home and study up on RCW 9.41.270
Or ask him to provide the state law that says OC is illegal.
Edit: as to the gentleman that asked you why you had to carry it. Tell him that you don't ask him why he wears a helmet on his bike. You don't ask him because you already know the answer, it should be thesame way with a firearm.