Why do you care if someone believes that what you play every night is NOT an instrument? Let them believe, as long as they pay you to play your non-instrument.

History is FULL of people that stubborny believed in ideas that were behind the times, with consequences that ranged from hilarious to tragic.

History is also full of people with ideas ahead of their time.

Both parties left a mark in history, but what party do YOU want to join?

Never ever get in an argument with an idiot, because there is no way to argue with an idiot.

Surely not the idiot argument where the xyz classical piano/violin/oboe/conga/timpani/banjo/whatever player/teacher tells me that my Casio and my PC (or anything that can be plugged in the wall) are not "proper/real instruments" and that if I wanted to do things right I should study 14 hours a day for 14 years to get a piano diploma.