So because he was gay is the only reason he was reluctant to fight him? Come on, do you consider friendship so low that it wouldn't have mattered. It seemed fine before this "Dumbledore is gay" stuff came up. It's not like it didn't make any sense before this news broke.
Chap, you of all people should know that it makes for a "deeper," more involved character if there's a love-story angle/conflict in the story.
It DOES change the dynamic of fictional characters. It just does. That's why Hollywood adds (forces, in some cases) a love interest in every damn movie.
I think the vast majority of people are interested in it because it's Harry Potter. People are obsessed with everything HP. Nothing more, nothing less. It gives these people a reason to go re-read the books through a new lens, with a different understanding of a central character's motivations and subtext.
JMHO.