Because of economic sanctions that China imposed on us two years ago, Australian businesses have learned to cope without its market for coal, wine, barley and other products. And that's the way it should stay.

China's students are returning to Australia and its tourists will eventually, but businesses that serve them had better remember that Beijing can easily cut off that source of demand.

Beijing's ambassador to Canberra, Xiao Qian, is urging faster improvement in relations under our new government. He suggests Australia could more easily afford tax cuts if it could get along with his country better - implicitly, because more trade would promote our economic growth and therefore public revenue.

No, thanks, Mr Xiao. We've already seen that lots of trade with China is a weapon that your government is happy to use against us. It's a weapon that China gets to use just once.

Our exporters driven out of China have found markets elsewhere, though they are surely making less money in them. After all, they were selling to China because that's where they had found the best profits.

Maybe some wouldn't mind getting back into China now. Except where quick money can be made by risking only a small outlay, they should forget it.

Actually, they should have been aware of the risks even before a diplomatic stoush in 2020 resulted in Beijing blocking imports of some Australian products. That view may seem harsh, since running an enterprise is difficult enough without being expected to keep an eye on international relations. But if you're in business, you are responsible for your own risks.

Admittedly, it would have been easier if our then government had not kept sending the wrong signals by absurdly promoting exports to China long after it should have recognised that we needed less economic exposure to that country, not more. It kept trying to enlarge China's trade weapon.

Incredibly, Simon Birmingham, then trade minister, was still running off to China as late as November 2019 to talk up our products. That was more than two years after the government had finally worked out that China was a threat.

While some businesses may feel they were misled by government signalling, one feels less sympathy for universities.

Last decade they erected ever more splendid campus edifices, in no small degree to cater for students we welcome from China. But in 2022 vice-chancellors must be wondering about the dependability of the Chinese education demand that is now slowly recovering from pandemic border closures.

One feels less sympathy for them because, at least in theory, they were uniquely placed to know whether Australia's relations with China could turn bad. They just had to pop down the corridor to ask their own academic specialists in the field. Either the uni bosses didn't consult their experts or they got bum steers from them.

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Just in case vice-chancellors are still not getting the right advice, let me offer a little. Next time the aggressive administration of President Xi Jinping is irritated by Australian recalcitrance, it can use any number of tactics to direct students elsewhere without even imposing an official ban.

Just for starters, it can concoct domestic propaganda about racism and even anti-Chinese violence in Australia. It can quietly direct intermediaries in China to promote unis in other countries. It might also obstruct foreign exchange transactions that pay for Australian education services.

Tourism businesses take note: much the same tactics can be used against you. When China finally reopens its borders, hopefully next year, we will again welcome its tourists, but they could disappear in a flash.

Our iron ore is an exception to all this, incidentally. China needs the stuff, and all the more when it's spending heavily on infrastructure to support a sagging economy, as it is now.

In return for doubtfully desirable economic benefits, Ambassador Xiao tells Nine Entertainment newspapers that Australia should stop making public statements about Xinjiang and Taiwan. He's referring to our complaints that China is committing human rights abuses in one and threatens to use force to take control of the other.

Our public comments are hurting the Chinese people, he says.

Chinese diplomats often use that peculiar line, usually with the full wording "hurting the feelings of the Chinese people."

It's supposed to put foreigners on the defensive, by making them feel embarrassed for causing offence to 1.4 billion people. But the usual foreign reaction is somewhere between confusion and giggles.

As the years pass, we're told of ever more things that foreign governments can't do or say for fear of hurting the feelings of the Chinese people.

Xiao would prefer that Australia made its comments on the Xinjiang and Taiwanese issues quietly through diplomatic channels - like that spineless wonder New Zealand, which still wants to protect exports that sooner or later will be used as a weapon against it.

Public discussion is "not conducive to creating a favourable atmosphere," Xiao says. Well, I can suggest something that would be: the release of Cheng Lei, an Australian who has been cruelly held in China on charges obviously contrived to punish us for displeasing Beijing.

If Xiao wants a better atmosphere to promote relations, letting Cheng go would be an excellent step to take.

Of course, we wouldn't expect China to demand some specific concession in return for her release. That would mean admitting that she's a hostage. China wouldn't want to be so blatant, would it? Or maybe it would.