When I see penis graffiti I normally assume some guy is asserting his dubious masculinity. By why, I have to wonder, was this specimen on the inside of a ladies' room toilet stall?
Assuming the artists does not actually own the equipment in question, I can only assume that they were going for shock value. And frankly, an anatomically accurate depiction of a vagina would be way more startling.
It was, at least, a well rounded toilet stall that covered not only sexual genitalia but also the (occasionally) associated emotions.