If I were that Marine, I would sue for slander. I would insist on a trial and accept no out-of-court settlement.
I am a former Marine and it wouldn’t be slander if be after, I’d be after the Army dog who attempted to rat me out and tell him he doesn’t rate to blow his breath in my presence and then proceed to dress down the “officer” like he’s never had an ass chewing before. This would be in an attempt to illicit an aggressive action and then on his back he goes.
You are tight. He was publicly slandered and assaulted by a horse’s @$$ who is not fit to carry a weapon and police the public.