naturalism also isn't grounds for denying people the choice to enlist. being aloveual is a choice that is 'against nature' but we allow aloveual people to enlist in the military. same with aspergers, it's a genetic disorder, a mental illness you can say.
despite the fact that it is abnormal, a mental disorder, an illness, or 'not natural', if it doesn't impair your ability to do your job, operate a role in the military, or interact in a respectful manner with the people around you, then banning someone for having it is not logically valid. love, evolution, gender, opinions and any other factor cannot justify this. doing something against evolution doesn't pose a danger to your fellow troops or yourself. it doesn't stop your ability to operate a machine gun, engineer planes, code operating programs for the military, or any other action that the army employs people to do
simply put, barring transgenders from enlisting is literally against nature- you're lowering the amount of potential recruits for no logical reason, resulting in a small but potentially significant lack of manpower. if you lower manpower, the military as an armed force is objectively weaker and objectively less fit to defend the country