I mean have these people ever read any ancient writings, like the Old Testament for instance?
The Hindu epic Mahabharata is an example -- the oldest epic in the world. Interestingly, the main story thread is about a transsexual woman. A summary of the story:
A beautiful princess is insulted by the greatest warrior in the world, Bhishma. She tries to get revenge, but fails; so she kills herself vowing to get revenge in her next life (a bit more complicated than that). Reborn a girl, but her father, because of a dream, raises her as a boy. When she is of age, she changes sex through a powerful mantra and becomes a man, but with a memory of the insult and the need for revenge.
Bhishma meanwhile has a divine boon that he cannot be killed until he himself decides to die. Nobody can kill him. During the great war of Kurukshetra, the "goody" side with Krishna, Arjuna and all the favourites is losing because Bhishma is on the baddy side.
Oh yeah, I forgot, the princess (Amba) has received a garland from the God Shiva which has the boon: whoever wears it will cause the death of Bhishma. Long story short, Amba, now in a man's body, has a showdown with Bhishma.
Now, warrior etiquette of the time is taken very seriously, and demands that a warrior cannot fight a woman, But Amba is a man now, right?
Bhishma, however, is very upright. He says that for him, a woman is not only a woman in a woman's body: also, a person born female, or a female in a man's body, is still a woman.
So he lays down his weapons. Amba, together with the great hero Arjuna, shoots the arrow that will kill Bhishma. And so, the goodies win the battle.
Male and female, the sex binary, invented by colonialists... truly we are living in a dystopian novel, that people, Cambridge students no less, should be entertaining such theories.
Tell me, did the colonialists also dictate a sex binary in animals? Did mammals only start mating when the white man came along? The hubris is breathtaking!