We the Mudbloods: long, heavily referenced, point-by-point refutation of Rowling's essay. NB. It's in three parts, with a link to part 2 at the end of part 1.
Video essay by a cis woman and a trans man (who are also partners). Quite user-friendly for people who aren't particularly familiar with the issues.
Video reviewing the Rowling's essay, and also discussing the ways it may or may not affect the reading experience of Harry Potter fans uncomfortable with the author's views.