One of the interesting things about street art, is that you never really know what the artist was trying to convey. Unlike plaques hung next to pieces in art galleries that describe intents, context, or back stories, unless it's something by Banksy a lot of the time street art is the domain of faceless people.
This piece is almost egging you on, calling on you to fire up about graffiti and 'kids these days'. It's humorous in a very cheeky way. Or so you might suppose.
It's also possible that someone just decided to scribble this onto a wall, for no real reason. One thing's for sure, they do have good penmanship.