The protests against parallel-goods traders last Sunday can only be condemned in the strongest terms. In yet another day of clashes in some districts, the activists crossed the line by targeting shoppers, cross-border buses and passers-by with suitcases and trolleys. The campaign has elicited outrage and contempt. It is as much an abuse of the right to protest as a challenge to the rule of law.

There can be no doubt that people's daily lives have been disrupted by the influx of mainland visitors, in particular those taking advantage of the travel convenience to do cross-border parallel trading. But that does not justify violence. Social media has been awash with videos showing incidents of insult and abuse. The protesters behaved like gangsters, storming into shops and yelling at customers. They also confronted passers-by who had trolleys and suitcases. They forced a Cantonese-speaking mother to open her suitcase, only to find that it was full of children's books. Her young daughter was frightened by the confrontation and cried helplessly. Another episode saw an elderly man being knocked over in a scuffle. It turned out the 73-year-old was only carrying his musical instruments home following a gathering with friends in Tuen Mun Park.

More disturbing is the defence of Civic Passion, one of the groups behind the protests. A group member said the public should not judge protesters with the "moral standards of a saint", adding that only through protests and chaos could the people's way of life be restored. It is true that grievances are on the increase, partly because the government is not seen as doing enough to tackle the issue. But anger and frustration are not excuses to break the law. Concerns are growing that the unruly behaviour will be repeated at Government House on its open day on Sunday. The community has to express its sternest disapproval at such uncivilised behaviour. Hong Kong has a fine tradition of expressing opinion in a peaceful and orderly manner. Those who have disrupted public order should be handled according to the law.