I don't think anyone here is talking about an uproar because DD is gay, or at least that was my impression, nor are they offended that he is.
For me it is about why JKR announced it the way she did.
- Why did she not do it in the Book (if, as you say, she knew it from the get go)?
- Was it valid of her at all to announce it after-the-fact like that, with the 7 books safely published?
- Did she know the effect/debate/etc... she would cause by doing so?
- Indeed, should she revise the Books & put it in?
Personally, I'm not much bothered. I love the story as it is written, I've re-read it all a few times and I expect to re-read it all a great many more. And Dumbledore will still be 'Dumbledore' each time I do.
... but there's no harm in a bit of healthy debate in the meantime?