On the paper's responsibility: On the one hand, this is a "personal essay," so readers should be aware Hale's views don't represent the official view of the Guardian. OTOH, if I, as a newspaper editor, received a submission like this, I'd have a LOT of questions for the author. I'd request corroboration of her statements about being mocked on Twitter, etc. I'd research STGRB to see how much credibility it has. Ultimately, if Harris or others who knew her told a different story, it would be time to kill that piece. You don't print hearsay just because it's culturally interesting.
Granted, they have used a pseudonym for Harris' supposed RL identity, but they've still given a platform to Hale's claims about her online persona.
By publishing the piece, the paper isn't necessarily condoning Hale's stalking, though one could argue it's validating that behavior by treating it as an episode of authorial quirkiness rather than a crime. What the paper is definitely doing is uncritically passing on Hale's view of GR as a shark tank where obscure, trolling vendettas can kill an author's career.
As I read, I found myself wondering, "Can that really happen? How often?" Since Hale's account doesn't reflect my own (limited) experience of Goodreads, I stayed skeptical while considering her claims. If I were a Guardian reader who knew GR only by reputation, I might have been swayed by her account, which was presented with no competing perspective.
Whatever the atmosphere on GR, all writers should be offended by the notion that expressing your feelings about a book frankly online is tantamount to harassing or trolling its author, or that the two actions tend to go together. Yes, opinions can be nasty, harsh and out of line, but It's a book. It's not a physical piece of you. If one reviewer is egregiously unfair, let other reviewers set the record straight. I've never seen a GR page where every single reviewer was in lockstep, and the range of reviews for Hale's book is a case in point.