There is NO evidence suggesting either soldier refused to obey an order. Both seen to be carrying out their duties.
It is perfectly legal to participate as plaintiffs in a suit. A person's right to sue is not abrogated by U. S. military service.

The soldiers are guilty of ignorance and/or stupidity (in my view) but neither is a courts-martial offence unless someone is hurt by their actions (i. e., negligent homicide and the like).

(Digression. Yes, the army has to deal with certain types of ignorance, but gross stupidity is generally dealt with by discharge ('at the convenience of the Army'). I remember, in WW2, youths from Mexico and on our side of the border, the hill villages of New Mexico, were admitted to the Army although they had little knowledge of English. I particularly remember how one sergeant, detailed to them, taught them. He collected all of the sex magazines and auto-truck repair manuals he could get his hands on. It wasn't long before the recruits picked up enough English to serve effectively. Volunteering for service was a quick way for an immigrant, legal of illegal, to acquire citizenship. Of course some were killed in action before they were discharged and received their papers).