It said diverse gender identities and expressions
aren't mental illnesses. Extreme distress in anyone is a mental illness. Depression and PTSD are mental illnesses. Being trans in and of itself isn't a mental illness but gender dysphoria (distress) can lead to mental illness and the treatment is affirmative care. Here's a bit more information from the people who write the diagnositic book on mental health.
Gender Dysphoria Diagnosis
With the publication of DSM–5 in 2013, “gender identity disorder” was eliminated and replaced with “gender dysphoria.” This change further focused the diagnosis on the gender identity-related distress that some transgender people experience (and for which they may seek psychiatric, medical, and surgical treatments) rather than on transgender individuals or identities themselves.
The presence of gender variance is not the pathology but dysphoria is from the distress caused by the body and mind not aligning and/or societal marginalization of gender-variant people. It needs to be ego-dystonic to qualify as a diagnosis and having a discussion with our patients about the diagnosis prior to charting it is necessary and good care.
The DSM–5 articulates explicitly that “gender non-conformity is not in itself a mental disorder.”
Well one, Marxism is an economic theory, it doesn't have anything at all to do with gender expression, and secondly, history and tradition are poor excuses for ignoring advancements in understanding.