Telling someone to mind their own business can be rude.
Steve is sitting down at the cafeteria lunch table and a fellow student Fred asks him what he brought for lunch.
Steve wants to respond to Fred's inquiry.
Steve tells Fred that his mother packed him a sandwich, carrots, grapes and a cookie.
Steve tells Fred to buzz off and mind his own business.
Fred is happy to hear the answer and continues to chat with Steve while enjoying his lunch.
Fred's feelings are hurt, and he goes to sit at another lunch table.