Self deprecating is just fine, I get that bit. It's when the term is picked up by others outside the group and used in a demeaning sense that it becomes unacceptable. The same principle applies to any profession. Whilst doctors may be quite happy to refer to themselves as 'quacks', 'pill merchants' etc they wouldn't welcome a patient walking through the door and calling them by these same terms.
I don't 'pilot' a bus any more than I 'drive' an aircraft.