Actually, it's not clever at all. It's dumb, embarassing, and makes both the person who says it and the person at whom it is directed feel like shit. Yeah, let's yell at each other on the street, and run around the corner to get away.
And here is a newsflash: this is spray. Everything posted here should be taken with a grain of salt. My posting about what to say to be truly rude, was more in line with what I would be thinking about those fat ignoramuses, but I would not actually say to them. Nor would I say what Gary said.