The way the press treats political leaders marks a crucial dividing line between free and authoritarian countries. In an authoritarian state, presidents and prime ministers demand and receive reverential treatment. In democratic countries, political leaders know that they will be subject to satire - and vicious and sometimes unfair criticism.
The case of Mr Jan Bohmermann, a German satirist, marks an attempt to export authoritarian practices into the democratic West. Last week, the German government announced that it will allow prosecutors to pursue a case against Mr Bohmermann for insulting Mr Recep Tayyip Erdogan, the President of Turkey.
It is possible to see this whole affair as a weird one-off - a product of the collision of an archaic German law against insulting foreign leaders with a touchy Turkish leader and a government in Berlin that, just at this moment, desperately needs the cooperation of Turkey over the migrant crisis.
In reality, however, the Bohmermann case is more likely to be a harbinger of things to come than an isolated incident - which is why German Chancellor Angela Merkel has made a mistake in allowing the prosecution to proceed.
The days when European governments were rich, powerful and proud enough simply to brush off threats from the likes of Turkey, Saudi Arabia, Russia or China are over. Europe's economic and political power is in relative decline. That makes EU countries potentially much more vulnerable to pressure from foreign leaders to rein in European media - or face the economic and strategic consequences.
The days when European governments were rich, powerful and proud enough simply to brush off threats from the likes of Turkey, Saudi Arabia, Russia or China are over. Europe's economic and political power is in relative decline.
The threat of international incidents provoked by the Western media is hugely amplified by the Internet, which ensures that an article published in one country can be instantly read on the other side of the world. The Turkish government has launched more than 1,800 cases against Turks accused of insulting President Erdogan. But the Turkish leader would also love to intimidate and punish his critics overseas.
If Europeans think that Turkey is in a uniquely powerful position because of the refugee crisis, they should consider the potential clout of China, which is wooing governments across Europe with promises of trade and investment.
Since President Xi Jinping took power in 2012, dozens of Chinese journalists have been imprisoned. More recently, Beijing has begun targeting critical writers and journalists in the wider world - sometimes by arresting members of their family resident in China. Western newspapers have also become familiar with heavy- handed interventions by Chinese officials displeased by articles on a range of subjects, from Tibet to official corruption. As China's economic leverage grows, so will its power to exert direct and indirect pressure on the Western media.
The West's ability to protect press freedom may be sapped, not just by economic pressure but also by political developments and moral confusion within Europe. The independence of the media has been seriously restricted in Hungary, whose leader Viktor Orban is an admirer of Asian authoritarianism.
At the European Press Prize awards in Prague last week, journalists from Poland, Slovakia and the Czech Republic expressed concern about threats to press freedom in their own nations, citing a mixture of government pressure and the purchase of newspaper groups by powerful oligarchs.
After the murderous assault on Charlie Hebdo magazine in Paris last year, the fear of violent extremism is undoubtedly making many editors think twice about the kind of material they publish. Meanwhile, the insidious pressure on university campuses in the United Kingdom and elsewhere to establish "safe spaces" in which students are protected from views that they find offensive also has implications for press freedom. The kind of obscene rhetoric used by the likes of Mr Bohmermann would undoubtedly violate any number of "safe space" policies.
There are voices in Germany and elsewhere saying that Mr Bohmermann's satirical claim that Mr Erdogan is a fan of child porn is indeed unacceptable, just as using a racial slur against US President Barack Obama would be taboo. It is true that press freedom, even in Europe, is never absolute. If criticism of a political leader crosses the line into outright lies, politicians can always sue for libel, an option that is open to Mr Erdogan in Germany. But it should not be acceptable for leaders to enjoy some special protection under the law that is not available to ordinary citizens.
Most European countries also regard racist speech as taboo and, in extreme cases, subject to prosecution. But there is a vital distinction between attacking a person or a group for who they are and criticising or satirising particular views or beliefs. It should not be acceptable to attack somebody simply for being a Muslim or Jew or gay. But the right to criticise religious or political views must be protected, even if some people and groups are inevitably upset by criticism of their cherished beliefs.
In the coming years, protecting press freedom is likely to cost Europeans contracts and money. It will cause diplomatic headaches and it will sometimes be dangerous.
If Europeans bend and compromise fundamental freedoms, they may gain money and a quiet life but they will lose their self-respect and, ultimately, the respect of the world.