Given how strident the author has been about her views, and that she is still a living person, earning royalties and materially contributing to anti-transgender causes, proclaiming oneself a fan of these books is as least saying that the author’s anti-transgender activism is not a dealbreaker. Making part of one’s identity an aspect of the books’ universe is even more so, to the point where there’s a correlation between people proclaiming their Hogwarts house in their bio and expressing anti-trans views. (TERF/“gender critical” activists having suddenly discovered that they were Slitherpuffs or whatever a few years ago, despite not having expressed any interest in YA fantasy novels before Rowling’s statements, is an observed phenomenon, to the point where such a statement in one’s bio is more likely than not to serve as a feeler for scouting out fellow anti-trans sympathisers.)