[wpietri]

The difference is that in your imaginary discussion, the person is proposing nuance informed by evidence. The comment you're replying to, on the other hand, pushes against nuance based only on personal opinion.

I don't know anybody who would argue that gender has absolutely no biological implications. But to suggest they tell us something about how society should be structured is the naturalistic fallacy, confusing is with ought.

As an example, illness and death are natural. But that doesn't mean that we should just shrug and say, "Oh well, tuberculosis is natural, so we should just accept it." The natural details of death should certainly inform how we fight it. But they can never tell us we shouldn't.