Like many, I was surprised to learn that Albus Dumbledore was gay. It was also interesting to see the reaction of those on the far-right. People talked of feeling betrayed by J.K. Rowling. People argued that she introduced politics into a children's novel series. Clearly, these folks haven't read any of the Harry Potter books, or paid attention to the commentary of the author. Rowling, first and foremost, made sure that her books reflected the importance of tolerance for the diversity of humanity (I mean this is a world with elves, goblins, trolls and hags, to name a few). She also made it clear, through her works, that she was not particularly a fan of authoritarian rule through government. Actually, the novels showed the shortcomings and out and out failures of government. Either way, politics have always been there.
Besides, it isn't as though Rowling decided that Dumbledore was gay at the time the questioner made his/her query. She has lived with these characters for more than a decade, so I am quite sure that Dumbledore has been gay in her estimation (imagination) from the off. And in all honesty, it's not that serious.