@EmbarrassingHadrosaurus different scenarious.
The equivalent to your hypothyroidism/ME/etc scenarious is if a claimant were saying, "I can't work because I'm trans. Being trans has these impacts on my ability to work..."
In that case, it's totally within his remit to assess whether there are medical grounds for their claims on how their gender identity impacts on their ability to work.
That's not what's happening here. Based on the tribunal information, he doesn't believe in transgenderism and has a conscientious objection to it, and bases this on the opening verses of Genesis. So he refuses to use people's chosen names and titles. He refuses to do so even if the reason they can't work is back pain, or cancer, or having lost a limb. So nothing at all to do with their gender identity.
His preferred solution is that he doesn't assess anyone who is trans.
He raised this in training. The DWP looked into it and decided stopping him seeing any trans clients wouldn't work for two reasons. Firstly, often the assessor doesn't find out that someone is trans til they're already in the room. Stopping the consultation saying, "I don't believe in how you're choosing to identify, so I'm not prepared to assess your bad back" is bound to cause offence. It also delays the person's assessment, as they'll have to wait for another assessor to become available, and may mean they have to come back another day.
Which may involve 3 bus rides. For someone with a disability. Where every penny counts.
How would we feel about an assessor choosing not to see a gay client because he is fundamentally oppossed to their lifestyle on religious grounds? Or a client from a different religion?
The DWP decided this wasn't okay, and so fired him.
The tribunal decided that his beliefs were "genuinely and ferverently held" and that he was entitled to hold them. They're very clear on that.
What he wasn't entitled to do was act on those beliefs in a way which he agreed trans clients would find offensive, and which would inevitably delay them being assessed.
I'm GC in my beliefs. I think sex cannot be changed and that single sex spaces are important. I'm willing to fight for those beliefs (and have dug in various gardens to do so).
I wouldn't dream of calling a trans patient - or any patient - by anything other than their preferred name and title. Because when I'm seeing a patient the consultation isn't about me.