In 35+ years, I only knew of one instance of the "Conduct prejudicial ..." being used. At the time of Suez, there were multiple troop movements around the ME and shortage of transport aircraft meant using Tudors (which had been banned from pax flying.) One of our aircrew ( a confirmed alcoholic and 'reggie spotter') witnessed the arrival, and, in well-oiled anxiety, informed the troops on board that their aircraft was unsafe. Their subsequent refusal to board for onward passage to Nairobi lead, eventually, to the 'whistle-blower' being charged, demoted and dismissed.