Here's how the coversation went in Carnagie Hall:
The question was: Did Dumbledore, who believed in the prevailing power of love, ever fall in love himself?
JKR: My truthful answer to you... I always thought of Dumbledore as gay. [ovation.] ... Dumbledore fell in love with Grindelwald, and that that added to his horror when Grindelwald showed himself to be what he was. To an extent, do we say it excused Dumbledore a little more because falling in love can blind us to an extent? But, he met someone as brilliant as he was, and rather like Bellatrix he was very drawn to this brilliant person, and horribly, terribly let down by him. Yeah, that's how i always saw Dumbledore. In fact, recently I was in a script read through for the sixth film, and they had Dumbledore saying a line to Harry early in the script saying I knew a girl once, whose hair... [laughter]. I had to write a little note in the margin and slide it along to the scriptwriter, "Dumbledore's gay!" [laughter] "If I'd known it would make you so happy, I would have announced it years ago!"
Excerpt taken from
The Leaky Cauldron.
I wrote the following in a previous post regarding this.
Well he is a hugely popular character. For those who are gay and/or are struggling with their sexuality might find comfort in that a generous man like Dumbledore is gay. This revelation may even pave a path of tolerance (if not acceptance) for many people who do/have/will read these books.
The person from GLAAD isn't wrong in saying that the portrayal of gay characters in media influences what people think of them (most of the things we do is influenced by the media) unless they know gay men/women personally or are gay themselves.
btw: The earlier kids learn about this stuff the better it is. And since this book is recommended for 8 and above people shouldn't even be using "but think about the kids" excuse as children by that age kids should know all about sex. If they don't know then some people are neglecting their parenting duties. Personally I think, most parents are neglecting that particular part of their parenting duties.