Art is as difficult to define as folk music, and a great deal of nonsense is bandied about on both subjects. I don't think we need to get involved in all that over a question like this.

My own experience, for what it's worth, is that people who go in for potentially offensive t-shirt mottos are immature but, on the whole, harmless. The real nutters are the ones who dress conventionally (except sometimes for funny little woolly hats). Avoid anyone wearing a balaclava; that goes without saying.