that he has no life and whatever he does for fun is a waste of time money and effort. Painting a dope ass huge peice on a wall is way more "real" than painting some stupid landscape on a canvas. And bombing is about getting up, beating the system, crushing societty, crushing capatalism etc. and plus its fun as fuck. A real graffiti head will experience way more than some normal kid who sticks to sports and plays video games for fun. Graffiti is not only fun but its also a great way to experience things and to see the world for what it really is. In my time as a writer i have seen more than any average 14 year old has seen. Graffiti is a good way to find yourself and to really have something to live for. Sitting in a room painting landscapes will build nothing and acomplish nothing. A graffiti lifestyle will be much more enjoyable than any normal lifestyle your freinds may live.
Just keep it up and dont stop no matter what your freind may say. Maybe even teach your freind about why graffiti is so great.