Why does the military get to discriminate against the transgender community? Is this even legal?

This question is the most recent culmination of a long line of military-related issues with the LGBT community that far pre-date the Trump Administration.  Historically, the military took the position that transgender people are medically unfit to serve.  Although case law is sparse, that justification was validated in Doe v. Alexander, 510 F. Supp. 900…