In fact so upset that they've gone and collected a pot of paint and a brush, driven into the middle of nowhere, and written this on an isolated farm building. You have to hope that the act of daubing the message provided some catharsis for the artist.
Just imagine him, or her, standing back and admiring their handiwork, head on one side and thinking that's perfect.
Could it have been a case unrequited love, a big quarrel, a neighbours disagreement or just a case of dislike?
Did they have the last word or is this the last word?
We'll never know, we just hope they don't still live next door to one another.