It is not a "vague demand" for evidence. Please see the Methodology section of the final report of the Cass Review for the detail of what is considered evidence-based medicine, both generally and within the context of the review: https://cass.independent-review.uk/wp-content/uploads/2024/0...

> but that's better than someone killing themselves or suffering without the quality of life they could have if they weren't denied.

Again, there isn't sufficient evidence to support this ideological viewpoint.