It's directed at those people who can't seem "get it all" in the toilet and leave the lid, floor, and walls covered in their biomass. The black duct tape is reminiscent of a person made of poo and is meant to tell such people that make messes that they're made of shit. The knee is white symbolizing that small part in us all that thinks about being clean and pure, bending to the needs of society if you will. Notice the bent posture and hand in the toilet paper holder. This is reminiscent of the praying to the porcelain throne that we've all done at some point due to the pain that's being inflicted by not having a clean toilet, or no toilet paper.