Accorrding to the report, it was one of the SOs, not the FO.
If he can't sort things out with the knuckle, a shrewd capt can always resort to "CRM" to mind-f**k the SO into feeling placated and shutting his yap. Looks like the capt dropped the ball on this occasion.
Capts being reported by the help, capts being gotten the better of by SOs... what next? The cleaners lodging complaints???