The problem is that once a whale gets run over by a ship, he/she will (somehow) tell the other whales that ships are "bad" and must be attacked. Then whales tell eachother that ships must be attacked, and this continues even after the original whale that got run over by a ship dies.
To be fair to the orcas, boats do seem to be awful for them. At the Seattle aquarium there's tons of information about how the noise from boats makes hunting much more difficult for orca pods. This was a sailing vessel but maybe they're unable to distinguish? Or maybe it was running it's motor, most sailing vessels of sufficient size have on board motors.
