In both cases, the perpetrators believe the absence of security and the unlikely prospect of intervention by members of the public mean they can get away with their abhorrent behaviour.
Much the same state of affairs applies in New Zealand. Racist taunting is highly unlikely to occur at Eden Park, but some people clearly feel they will not be confronted at lower-level matches. That is a severe indictment of the other spectators at these games. This behaviour would not be possible if they voiced their disapproval at the time or, at the very least, reported the culprits after the match.
In the case of the fixture between Saracens and Hampstead, that did not happen. After an investigation, the North Canterbury sub-union said it accepted there had been racial abuse, but ruled there would be no punishment for Saracens because the culprit or culprits had not been identified.
That is a societal failing, not simply a black mark for rugby. As the Race Relations Commissioner, Dame Susan Devoy, noted: "All of us - not just officials - are responsible for standing up to people who use racism to win in sport." There is no point in deflecting blame by calling for referees to be more active, or excusing racist remarks as the product of the heat of the moment.
In the latest incident, the Canterbury Rugby Union and the Lincoln University club, Christchurch's opponent in the final, have, again, been unable to identify the perpetrators of the abuse. The matter has, therefore, been referred to the police for investigation.
This episode must not end with another limp statement, the consequence of not one of the spectators or, indeed, the culprits having the moral courage to come forward. There can be no cover-up and no hiding place. The culprits must be named and shamed at the appropriate time. Exposing the hurlers of racist abuse to the harshest public scrutiny is the surest way of eradicating this scourge once and for all.