As far as number 16 and 9 go... Well, the language I'd use towards anyone who said those things to me isn't appropriate for this forum. I've had piercings and listened to heavy metal for over half my life now and those aren't things you just grow out of.
Things everyone, everwhere needs to stop doing - telling others how to live their life.
I'd also add that out of all styles of music Metal and Classical are the most closely related. If you have a chance Google Rachel Barton Pine. Notice the part where she's a world renowned violinist that tours all over the world who also moonlights in a Heavy Metal band.