I think what this shows is a further incident of a point someone made about a recent case involving Sheffield's NHS Trust involving discrimination, which is that the law is getting the comparator entirely wrong when it comes to discrimination on the grounds of gender reassignment. What Mermaids and many other organisations are arguing is that in not treating a female like a male (in this case a gay organisation being allowed to exclude them on the basis of being female), they're discriminating against them, because they're not treating them like a man. But that isn't, or at least shouldn't be, the comparator for gender reassignment. What it should be is, are they treating her the same as anyone who doesn't have that characteristic, in other words, are they treating her the same as they would any other woman, who doesn't have the characteristic of gender reassignment. That's how it is for any of the other protected characteristics (bar maybe disability, where you can discriminate by not providing adequate accommodations) and that's how it should be for gender reassignment too.