People in bands can't be called a "celebrity"? but a "Rock star instead"?

personally I think it can be either. My friend picks stupid arguments with things like this with me and I have to ask these questions on here to prove to him how stupid he is. A celebrity is a famous or well-known person. People in certain bands are famous and well known, therefore they are a celebrity, Dave Grohl from foo fighters would be a celebrity, Paige Hamilton from helmet would be a celebrity, Angelo moore, front man of Fishbone would be a celebrity, am I right!? What do you all think?