Mark said:To the contrary, he is an exemplar of what a gay person can be as an instructor, mentor, and wizard.
I disagree. As it stands in the text, he is an exemplar of what a person can be, without reference to sexuality. That's kind of my point - reading the text, there is no allusion to his sexuality, so that isn't part of the character displayed to us. Rowling could just as plausibly said he was hetero, or just not interested in sex and romance.
If the only way to know about it is to step outside the text, then he can't be an exemplar of the type.