GEERT WILDERS, a Dutch politician, says some horrible, inflammatory things. He has called Islam a “fascist ideology” and referred to Muhammad, Islam’s prophet, as “a devil”. He is no friend of free speech, either: he wants to ban not only the Koran but also preaching in any language other than Dutch. The Economist deplores his views; but he should be allowed to express them.

Wild thing, you make my heart sink

Prosecutors in the Netherlands have reached a different conclusion. On December 9th a court found him guilty of insulting and inciting racial discrimination against Dutch Moroccans. At issue was a nasty line from a speech in 2014. “Do you want more or fewer Moroccans?” Mr Wilders asked supporters of his anti-immigrant Party for Freedom (PVV). The crowd replied: “Fewer! Fewer! Fewer! Fewer!” Mr Wilders smiled and said, softly: “We’ll take care of that.” The audience chuckled.

The court decided not to impose a fine, arguing that the conviction itself was punishment enough. Some punishment. Three months before an election, Mr Wilders can pose as a victim of an illiberal law and a politically correct elite who, he claims, are letting Islam undermine Dutch civilisation. Mr Wilders’s image as a martyr is further enhanced by the fact that Islamist radicals have threatened to kill him for his words.

All this makes him stronger. His party leads the polls, with the support of a third of voters. The PVV will probably not win control of the country—mainstream parties will club together to keep it out of office. But using the law to attempt to silence Mr Wilders enhances his malign influence over Dutch politics and makes it more likely that he will one day wield real power.

The Netherlands is far from the only democracy to criminalise “hate speech” that denigrates racial, religious or other groups. Such laws have widespread support, but they are misguided. Free speech is the oxygen of democracy—without it, all other political freedoms are diminished. So the right to free expression should be almost absolute. Bans on child pornography and the leaking of military secrets are reasonable. So, too, are bans on the deliberate incitement of violence. But such prohibitions should be narrowly drawn.

Standing outside a mosque shouting, “Let’s kill the Muslims!” qualifies. Complaining that your country has admitted too many migrants of a particular nationality does not. People should be free to debate immigration policy. Advocates of a liberal approach, such as this newspaper, should try to persuade those who disagree with them, not lock them up.

Proponents of hate-speech laws argue that they foster social harmony by forcing people to be more polite to each other. The opposite is more likely to be true. Criminalising something as subjective as the giving of offence encourages more people to say they are offended, so they can use the law to suppress views they dislike. This enrages those who are silenced; hardly a recipe for social tranquillity.

Such laws also provide an excuse for autocrats to censor their critics. China uses laws against inciting ethnic hatred to trample on Tibetans who demand autonomy. In Saudi Arabia and Pakistan anti-blasphemy laws are used to terrorise minorities and settle private scores. In all these cases censorious governments cite similarly worded Western laws as precedents. Enough. Governments should stop trying to police politeness. It stifles debate and helps bigots like Mr Wilders.