I'm not sure exactly what the warship was doing, and quite honestly if he'd sounded five blasts I would be taking avoiding action PDQ, not arguing the toss.
There have been tragic instances where a ship, for whatever reason, hasn't seen a small vessel and a collision has occurred, but in this case it's pretty obvious the warship was attempting to get the yacht to change course. This couple were being stubborn and pig-headed (much like motorists who stay in "their" lane and refuse to move over, regardless of the consequences, for someone who's inadvertently or carelessly drifted into their path).
If I recall correctly, the wife said yachts under sail can't turn round quickly; thousands of yachtsmen and women would tell her they absolutely can - unless they're stately galleons à la Joyce Grenfell.🙄