Re: What do you do when a student is acting rudely in your class.
He "said" that he was promoted to yudansha. Does he have evidence that he indeed has attained Dan ranking. Can he provide it? It looks like you gauge his aikido as sub-par.
Clearly he does not understand the kohai-sempai-sensei relationship in a dojo.
You must make him remember.
If he still insists to train with you and if he can't produce evidence of him being a yudansha, if it were me I'd tell him to start out as a 7th kyu to teach him about proper etiquette if he wants to continue training. If he doesn't agree, ask him to train in another dojo.