I agree that people shouldn't talk about it during their interview, especially for over half of it. It should be "what is your sexual orientation and gender identity?" (More specifically if they offer badges that say your gender identity, if you're in a customer-facing role, and you're comfortable wearing said badge), then the candidate should answer, and that should be the end of it. I would never dream of talking about my personal life unless specifically prompted to, and even then, I'd keep it to a minimum because it isn't relevant to the job.
Like I said, however, it is relevant if someone specifically chooses not to hire someone based on their sexual orientation or gender identity. That's discrimination. I'm not sure on the legality of the next part, but I don't believe it's discrimination to not hire someone because they're talking about things irrelevant to the job.
Again, I apologise if I'm not writing clearly - I don't relay things very well over text.
Also, in case it isn't obvious (due to the above reason I've just stated), I'm not slating you or saying you're incorrect. I am genuinely enjoying this discussion. I like to hear other people's viewpoints.