If I write a horror story and someone is disturbed or depressed by it, am I supposed to say "Maybe I shouldn't have written that"?
If you're writing horror, then the depressive elements aren't needless. If you're writing social commentary, then the ________ elements aren't needless. With the remark you quoted, I'm specifically referring to things like, for instance, stereotypical portrayals and other baggage-causing things that are needless towards getting the impact of your story.