Actually you are incorrect; even in adminstrative proceedings, the UCMJ provides the framework for determining any violations. I could not have held Office Hours/Article 15 without citing the specific violation under the UCMJ.
I am of the opinion that the Marine Corps overeacted to this Marine's case because of the publicity in the Navy/Marine Corps Times and the hyper-political sensitivity of our current leaders. In my opinion, all of this should have been handled at the battalion commander level and limited to NJP, Page 11 entry, reduction in rank - with the obvious preclusion from reenlistment.
That way Sgt Stein would have served as an example but been eligible form Veteran's Benefits, security clearance, employability. Our current leadership chose the "show trial" route to impress the administration, I guess. If I would advise him, I would recommend petitioning the Naval Board of Records to upgrade his discharge.
You would be correct if he was facing Art 15 proceedings, but this was an admin discharge board. Different animal.
What branch did you serve in? Marine Corps here.
Now that you mention it, I’m surprised he didn’t go to NJP first. Usually admin discharge is a last resort, not a first option.