Narrative therapists are often interested how people define themselves. They wouldn't challenge someone's identity per ce, but would explore with them how their perception/identity is impacting on them.
For example, for some, 'I am autistic', 'I have autism' and 'I have a diagnosis of autism' can be experienced as 'much of a muchness'. For others, there may be a significantly different lived experience from using different phrases. Sometimes, challenging and changing our narratives can improve the quality of our lives for the better.
Some people feel liberated by a diagnosis of autism, some feel oppressed. For some saying 'I am autistic' helps them to understand themselves better. They see autism as part of who they are and find the diagnosis helps them make sense of themselves. Some feel it important for autism to be relegated to a disorder that impacts on their lives, but is not part of their identity, so 'I have autism' helps to achieve this. Others feel oppressed by the diagnosis and reject it. For them, 'I have been given a diagnosis of autism', or ' I meet the criteria for being diagnosed with autism' would be a healthy and balanced narrative. A narrative of 'I have been coercively assigned autistic' is unlikely to be a helpful or healthy narrative as it is likely to lead to narratives that result in feeling oppressed. It also gives power to the idea that a diagnosis must be part of their identity. It also ignores a dominant narrative in society about autism existing and being significant.
Narrative approaches are based on the idea that humans are compelled to make meaning of ourselves and the world around us. We can't help but 'story' our lives. Our stories are our realities and we tend not to see them as stories or as being open to change.
Narrative approaches suggest the sometimes our stories of ourselves sit comfortably with dominant stories in society (what society holds as universal truths), sometimes they don't.
In narrative terms, Cashman's story seems to be that everyone should accept other people's story of who they are. Whilst he seems to recognise that some people's stories undermine others and that this is problematic, he seems to be selective in how he applies this.
He advocates accepting people's storied identities when it comes to identifying with gender. What about the storied identity of being defined by sexed bodies?
We need language/labels that properly communicate the difference between adopting an identity based on gender or on sex so we should allow both. I can't see any harm in people specifying a preference. We just need to make sure that there is room for both and a distinction is drawn.
Sex protections are needed, as are protections relating to gender identity.