No one should underestimate the strength of feeling among many Chinese people over Japan and the Diaoyu Islands. Japan took the islands around the end of the 19th century when the country was expanding aggressively, winning wars against China and Russia and occupying Korea and Taiwan.
Half a century later, Japan was expanding further, taking parts of mainland China and eventually much of Southeast Asia. Even today in Hong Kong, the "three years and eight months" of Japanese occupation is part of the city's collective memory. We all grew up hearing stories of Japanese atrocities. Tragically, some Japanese politicians and activists still deny that these horrifying events took place.
In Europe, most people accept Germany as a productive country which makes a positive contribution to the region. Japan does as well, yet many Asians still see the country as marked by the past.
Politicians and others might sometimes be tempted to exploit anti-Japanese feeling for their own purposes, but the fact is that they can do it because those feelings are so real and powerful.
The violence that broke out in dozens of mainland cities in the past week cannot be justified in any way. I would not be surprised if some of the people burning and looting had other frustrations or motives. But those who were genuinely angry at Japan seemed to be a clear majority. The vandalism was not just dangerous and illegal, but totally illogical.
Being involved in the insurance industry, I would point out that even if you could justify burning a Japanese restaurant or a Toyota-brand vehicle, you are still hurting innocent parties. For example, the Japanese restaurant is probably insured by a Chinese insurer or reinsurer, who will pay a claim, and who will then raise premiums for the restaurant.
In a world that has undergone globalisation, what is Japanese about a Toyota on the mainland? It was made in China by Chinese workers, as were many or even most of the components. If the car factory closes down because of threats of violence, who do the rioters hurt more - Chinese or Japanese? The answer is both, as the shareholders are probably mostly Japanese.
But their loss will be relatively minor. A shut-down factory will hit the economy of a whole Chinese neighbourhood or city. And who is the car's owner, watching her vehicle burn? A fellow Chinese.
Calls for boycotts of Japanese goods are similarly misguided. Even if the goods are actually made in Japan, a boycott hurts the distributors and vendors in China, whose employees are Chinese, who have families to support.
And it damages the suppliers of the Japanese company, many of which will probably be located in China. Open up any gizmo made by Sony or Toshiba and you will find components made by companies based in Taiwan, Korea, the United States, Germany and other places.
If they were not manufactured in those places, they were probably made in China by Chinese people. If you don't hurt Chinese people, you still hurt the Koreans or Germans - why?
Of course, even if you can find a way of hurting the Japanese and no one else, it is still wrong to do it. A Japanese resident of Hong Kong or on the mainland is not to blame for this situation, and we would hate to think that the many Chinese living in Japan might be threatened.
The fact is that globalisation makes it impossible to isolate people and places. Many Chinese and Hong Kong companies - including mine - have Japanese business partners.
And this is not just about trade and manufacturing; Japanese and Chinese people work, study and live together, and marry and have families.
This is a year of political change. Politicians in Japan, the US and China all need to be seen to protect their own country's interests. The result is a competition of rhetoric and gestures, not only between domestic factions contending for power but between governments, with the press and the public joining in. It is in all our interests that things calm down before long.
Bernard Chan is a member of the Executive Council