If someone does not identify with either gender then 'they' is the only accurate option.
Rhiannon, in the thread on male genital mutilation, where the subject is about boys and penises, there are a number of instances where the natural and obvious "he" or "his" have been replaced by "they" or "their". I wrote, earlier
where the context is solely and clearly male or female.
And "gender" is not the same as "sex" - sex is a binary condition, male or female, gender is a more complex and varied condition involving a continuum with masculine and feminine as its end points.
I'm not really trying to have a go at you, Rhi, it's just that I like language which is precise. (I only wish that I could always achieve my own standards
)