You know, the inevitable dumb one.
If there are more than two sexes, name a third one.
The correct answer is, obviously, “Your mom.”
But seriously, if I tell you something is a range or continuum, you don’t refute me by telling me I have to name every shade. When I was a child, I learned that there are 7 colors, precisely 7, in the rainbow: red, orange, yellow, green, blue, indigo, violet. Then when I got older I learned that there are hundreds of wavelengths between 400 and 700 nanometers. And then when I got older still I learned that color is the product of combinations of wavelengths, like chords, and the numbers got larger still. And then I learned about photoreception and color vision, and discovered that colors were a property of visual processing derived from context and relative distinctions in illumination and intensity, and there’s nothing fixed about them. I read David Marr in the 1980s, you know.
Then someone comes along and insists that the stuff they learned in kindergarten is the absolute rock solid truth.
Hey, I bet you this person is also one of those who mocks the abbreviation LGBTQIA+ because there are too many letters in it and we keep adding more.