Few years ago I participated at an international stage. In that time I was 1 kyu and accordingly with our Iwama's school regulation I was wearing an white belt. We were practicing jo suburi and a guy near me wearing a brown belt was doing very bad, pushing the jo without sliding but just gripping it very tight and moving it like pile driver. I told him in a polite tone that he is doing it in a wrong way. He looked at my belt and says " who the fuck do you think you are, a sensei??"
Oh the stories:
Beginner: "Oh good, we're all beginners, here. How many weeks have you been training?"
Me: "About seven years."
My mate, a Karate instructor: "Where's your belt?"
Me: "I'm wearing it"
Mate: "No, your brown belt"
Me: "I don't have a brown belt; there are only white and black belts in Aikido."
Mate: "Why's that?"
Me: "In okinawa belt mean no need rope hold up pants"
Beginner to me: "I don't take instructions from white belts"
Sensei: "You take instructions from 1st kyus"
Beginner: "Eight years and you're STILL a white belt?"
Me: "Actually I should take black belt next year......."
Beginner: "But you're a white belt?"
Mate: "He's a fast learner."