[andrewflnr]

This is where we get to goals rather than facts, but I'd argue that trying to second-guess gay people's sexuality is a distraction. The moral principle is to let consulting adults do what they want, as long as they're not hurting anyone. Nothing after that needs to matter more than a bar conversation.

(Yeah, that probably sounds like moving the goalposts. In a lot of cases the goal will be implicit and you can just talk in your debate partner's languages of "supposed to", and that's the situation I was imagining in my first post. But if it gets messy, then yeah, you'll need to get explicit about is-ought.)