I don’t remember joining the Army as being enumerated as a constitutionally protected right. They discriminate against fat people, people who do badly on the ASVAB, people with some pretty random medical conditions... I knew a guy who couldn’t get in because he was born with only one ear. They were OK with him being deaf in one ear but insisted he had to have two ears.
On the other hand Sikh’s have served with distinction in the British Army for a very long time and they have always worn turbans while doing it. If there is anything in their religion that precludes their being loyal to the United States, as there is in Islam, they should not be allowed in the armed forces anyway, but I’m not aware of anything like that.
if they cannot wear the same uniform, they could go join a different army
You seem to know your history. Posters against Sikh’s wearing beards have no clue about the British military experience with Sikh soldiers.
Just wait until the ADA applies to the Rangers.
Chairborne Rangers lead the way!