Race, sexual orientation, psychosis are all different issues.  To compare and contrast race (ethnicity) w/ sexual orientation is a strawman argument.  You can't choose to be black.  You can choose to be gay; or straight.  If what you mean is what are those characteristics that disqualify someone from military service?  There are many.  Ask a recruiter.  It could be financial, it could be criminal record, it could be affiliations w/ known orgs that hate america...not liking a hiring policy?...there are processes to change it.  This venue is not one of them.  Congress employs, Exec deploys, then checks w/ Congress before 90 days or so, so that the check and the balance is daijobu.  Obama allowed transgenders via his "power" as President, Trump can disallow it via his "power" as President.  If the SecDef one day decides that only left handed pilots can fly attack planes because left handed people feel marginalized from society..........!!!