The Church doesn't ordinarily make judgments about works of literature, leaving that to Catholics informed by their faith and by the discipline of literary criticism.
Given that, I can only offer my opinion, but it is one that is informed by having read all seven books in the Harry Potter
series and by having followed Christian concerns about the series.
Both reactions you report are, in my opinion, misguided. That Christian critics of the series would jump on this announcement as "proof" that the series is "morally bad" demonstrates that those Christians who make this argument likely have not read the books at all, or at least have not read them with open minds. In the books, Dumbledore's sexuality is not mentioned at all
. In retrospect, looking at the books in the light of Rowling's revelation, there are hints (e.g., Dumbledore's occasional effeminate affectations), but those hints can be interpreted in alternative ways. For example, since Dumbledore is the series' "wisdom figure," his feminine affectations can be interpreted as a symbol of his embodiment of both masculine and feminine wisdom (thus making him what might be called "fully wise").
On the other side, some fans of the series have entirely dismissed Rowling's revelation, saying that her understanding of her character is no more important than their own since she did not include this revelation in the series itself. That, I think, is disrespectful to Rowling and to her work in creating this character. Artists' creations are first their own and only secondarily their audiences. While a reader can provide his own insights into a literary work, those insights should conform to either what the author has revealed about the work or, if it is on a point that is open to interpretation, should not be in contradiction to the work itself. To completely dismiss an author's understanding of her creation is to lose valuable insight into the creation and to diminish the creation itself.
In this case, such dismissal is also entirely unnecessary. Since Dumbledore's sexuality plays no part in the series, parents are free to concentrate on other aspects of the series with their children, leaving this particular facet of the story unmentioned. If it does come up, perhaps because the child has heard of Rowling's revelation from news reports or from friends, a parent can then show the child how Rowling has left the series itself open to the understanding that Dumbledore never acted upon his same-sex attraction, but instead devoted himself to service to the community and to fighting evil. Such an understanding of the character can provide a fictional model of how those afflicted with SSA should seek to live. And, even if this is not Rowling's understanding of homosexuality, it is not contradictory to the series as she wrote it.
The Mystery of Harry Potter
by Nancy Carpentier Brown
Looking for God in Harry Potter
by John Granger