I believe the problem is never showing evidence, but that the evidence is overwhelming. I could explain the general idea and, maybe, one or two specifics. People that use the XX/XY binary argument wouldn’t be able to explain either, but it’s usually only used because it conforms to a bias. And we are only talking about humans here. Language would implode if we tried to maintain convenient binaries and still back it up with science.
A good image to have if a discussion about “men in women sport” breaks out. I heard so often: if XY then Man.
The whole spectrum of intersex is too complicated for the average today joe…
And then comes the even more complex topic of transgender people and gender affirming care/therapy, which can be a totally separate thing besides the intersex-biology-discussion