I actually know a trans theologist and she can talk for hours about both biblical and apocryphal sources for why it's every good Christian's duty to abolish the gender binary. Found that a lot more convincing than this papal nonsense, too.
How does this pathetic old man come up with the idea i was created with the wrong gender to begin with? There's nothing wrong about being trans. I'm fine the way i am, transitioning is a central part of my being, it can teach people a lot about the human condition, how we relate to ourselves as gendered beings, how seeing beyond such boundaries can be deeply liberating, but also how performing gender can be a source of joy and creativity and bring a bit more light into this world. There's beauty and grace in my existence, and the temporary discomfort that comes with it can easily be seen as my cross to bear from a Christian perspective, as suffering i'm virtuously enduring on my way to salvation. It's not very hard to see why God would have created me this way at all. In fact, it's much more of a stretch to deny me God's grace, even when one is short-sighted, one might say: transmedicalist, enough to see my gender as flawed - it was news to me that Catholicism now casts out people who were born in ways that society considers flawed, that's ableist as fuck, are we doing eugenics now, Francis? Your church wasn't even down for that when it literally supported Adolf fucking Hitler or upheld the institution of slavery, Christianity was always about healing people, Jesus was always there for the sick and lame, why doesn't that extend to gender incongruence? Spoiler: Because misogyny.
When both men and women are created in God's image, what does that tell us about God's gender anyway? Or is Francis actually saying that only men are created in God's image, because honestly, this nonsense isn't even internally consistent unless you say "there's only one correct gender and it's cis man, there's something inherently wrong about being anything else, something inherently evil about womanhood, so by extension there must be something inherently wrong about transness, as that automatically puts you outside male supremacy in some way, either by AGAB or by gender identity." Which is what he actually believes, but he can't say that part out loud because women make up half of his followers and a lot of them are fed up with being treated as second class human beings by the Vatican. So he needs to paper over these inconsistencies, pretend that at least cis women are accepted by him when they obviously aren't, and to pull that off, he needs to cast out those that traverse the lines between genders, those that demonstrate by their very existence that gender isn't that meaningful of a distinction, and by doing that he automatically denies the universality of human dignity and the promise that we will all be one in Christ.