Why should we be surprised that Lowry had a dark side? As an artist, it's a natural part of the terrain

What do we mean when we talk about an artist’s dark side? And why are we so surprised when we discover he has one? You think we’d know what to expect by now. Larkin a racist. Percy Grainger into S&M. Eric Gill a domestic pornographer. Dickens a louse to his wife. Tut, tut! And that’s before we talk about the art.