Art is any form of expression, why does it have to be a painting, music or acting?
By putting himself behind a mask and doing what he did, that's no different than street-art or poetry readings. Granted it's an incredibly graphic way of doing it but I still think it's a genius way of expressing himself. Take it how you will.
As I said, I don't understand making people drink his piss; making he thought it would give them a sense of feeling as gross as he thinks he does every day. Or maybe it was his way of connecting everyone?
Or maybe it was just completely and sick and the most disgusting thing he could think of?