I'm a little confused by this: Did the Human Rights Campaign say that in relation to Manning's case? What makes her gender reassignment surgery medically necessary?The Human Rights Campaign — an advocacy group for gays, lesbians and transgendered people — said there is “a clear legal consensus” that the U.S. government should cover the cost of sex-change operations for federal prisoners if the treatment is medically necessary.
Gender dysphoria is a formal medical diagnosis, and a combination of HRT and reassignment surgery are often the proscribed remedies. A failure to apply these procedures to a diagnosed individual requesting their application is simply a failure to provide medical treatment. Normal federal prisons provide these treatments, I don't know why the military thinks it's different.