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??"
In my opinion, belt colour has no actual importance, level of technique executing ability has! The guy you mentioned was obviously an impolite person with no manners and a huge ignorance of etiquette. But in a real fight, where it really counts, verbal offence won't help him. Or the colour of his belt for that matter...