One of the fellows I talked with phrased it like this. "If you met someone who was, by all standards your perfect partner, appearance, personality, interests, everything except the sexual organs, wouldn't you be pretty stupid to reject the possibility of a perfect relationship?"
I mean isn't the response to this that they're clearly not your perfect partner? Sex is a very serious part of romantic relationship, I can't imagine being with someone, not having a full filling sex life and pretending its a perfect match.
Imagine a straight woman who wants to be a mother answering this question. They find the perfect man, perfect partner, appearance, personality, interests, everything except the sexual organs, they don't have a penis and don't produce sperm, and thus can never father a child with her. I don't think she would describe that as the perfect partner. What you're describing in a perfect plutonic friend, because if you're not interested in having sex with them, what they have for sex organs isn't a concern.
To be the perfect partner for you I think we have to assume they have the sex organs you want to have sex with, and vice versa. Otherwise "perfect" just doesn't apply.
Just change any one other aspect and you'll see what I'm talking about: perfect partner, sex organs, personality, interests, everything except you can't stand the sight of them
perfect partner, appearance, sex organs, interests, everything except you can't stand their personality
Suddenly they're a lot less perfect