'A lack of belief in transgenderism'??
Disbelieving that humans can change sex.
The thing is, though, that he was fighting this specifically on the grounds that the tenets of gender identity ideology conflict with his Christian beliefs - he was arguing that his employer was trying to force him to profess something that he doesn't believe, rather than that they were trying to force him to profess something that isn't true (which is what was actually happening).
The difference is critical and this is what worries me about not only this ruling, but about Maya Forstater's case and any legal challenge that seeks to cast the factual position (humans can't change sex) as a 'belief' akin to a religious or political conviction, instead of a scientifically demonstrable truth.
In Australia recently we had the case of rugby player Israel Folau, who was sacked after he posted a meme on Facebook that said that homosexuals, fornicators, liars, thieves, atheists and idolators were all going to Hell. It was the 'homosexuals' bit that got Folau sacked, as Rugby Australia said he had breached their anti-discrimination policy (or, in today's jargon, their 'inclusion' policy, natch). He is now taking them to court for discriminating against him for expressing his Christian beliefs.
He might win, but he could just as easily lose, because Rugby Australia do have a strong case, I think, that in expressing this particular belief, Folau was creating a hostile environment for his gay colleagues. The court may well find that the employer-enforced position that gay and lesbian people are welcome in rugby should take precedence over Folau's right to express the fundamentalist Christian position that they are going to Hell.
Unlike the trans debate, the Folau case really IS a matter of conflicting beliefs. It's a political opinion that gay and lesbian people have the right not to be impugned because of their sexual orientation, and Folau's position that they are going to Hell is just that - a belief or opinion, with no basis in fact (no one can demonstrate that Hell exists, let alone which people will be going there).
The so-called 'GC' position is not at all akin to a religious belief. It's a provable fact that humans can't change sex, like the fact that we need oxygen to breathe. It's a reversal to claim that this is a 'belief', when it's the trans position that relies on evidence-free opinion and faith-based mantras. The fact that humans can't change sex is no more a belief than the fact that we will die if we don't get enough oxygen. Both are simply observable facts about human biology. And it creates all sorts of harm to pretend that fundamental properties of human biology don't exist.
I feel like these legal cases (including, unfortunately, Maya's), play into this reversal. If we frame the reality-based position as a 'belief' we will inevitably lose because courts and other authorities will, as they have here, decide that the right to express this 'belief' doesn't outweigh the trans-identified person's 'right' to have their false belief validated.
I think rather we should argue our case on the basis that what we say is TRUE. Sex is real and socially relevant. It impacts on our lives in many ways, and trying to deny this - or worse, forcing people to deny it - causes real harms, as the judge in the Freddy McDonnell case found.