W HO IS THE greater threat to free speech: President Donald Trump or campus radicals? Left and right disagree furiously about this. But it is the wrong question, akin to asking which of the two muggers currently assaulting you is leaving more bruises. What matters is that big chunks of both left and right are assaulting the most fundamental of liberties—the ability to say what you think. This is bad both for America and the world.

The outrages come so fast that it is easy to grow inured to them (see article). The president of the United States calls truthful journalism “fake news” and reporters “enemies of the people”. In June, when a reporter from Time pressed him about the Mueller inquiry, he snapped, “You can go to prison,” justifying his threat by speculating that Time might publish a picture of a letter from Kim Jong Un he had just displayed. Mr Trump cannot actually lock up reporters, because America’s robust constitution prevents him. But his constantly reiterated contempt for media freedom reassures autocrats in other countries that he will not stop them from locking up their own critics. On the contrary, when Saudi Arabia blatantly murdered Jamal Khashoggi, a Washington Post contributor, in its consulate in Istanbul last year, Mr Trump was quick to reassure the Saudi crown prince that this would not affect any oil or arms deals.

Campus radicals are less powerful than the president. But he will be gone by 2021 or 2025. By contrast, the 37% of American college students who told Gallup that it was fine to shout down speakers of whom they disapprove will be entering the adult world in their millions. So will the 10% who think it acceptable to use violence to silence speech they deem offensive. Such views are troubling, to put it mildly. It does not take many threats of violence to warn people off sensitive topics. And although the left usually insist that the only speech they wish to suppress is the hateful sort, they define this rather broadly. “Hateful” views may include opposing affirmative action, supporting a Republican or suggesting that America is a land of opportunity. Mansfield University of Pennsylvania bans students from sending any message that might be “annoying”. In some Republican states, meanwhile, public universities face pressure to keep climate change off the curriculum. Small wonder most American students think their classmates are afraid to say what they think.

As societies have grown more politically polarised, many people have come to believe that the other side is not merely misguided but evil. Their real goal is to oppress minorities (if they are on the right) or betray the United States (if they are on the left). To this Manichean view, campus radicals have added a second assertion: that words are in themselves often a form of violence, and that hearing unwelcome ideas is so traumatic, especially for disadvantaged groups, that the first job of a university is to protect its faculty and students from any such encounter. Some add that any campus official who disputes this dogma, or who inadvertently violates the ever-expanding catalogue of taboos, should be hounded out of their job.

These ideas are as harmful as they are wrongheaded. Free speech is the cornerstone not only of democracy but also of progress. Human beings are not free unless they can express themselves. Minds remain narrow unless exposed to different viewpoints. Ideas are more likely to be refined and improved if vigorously questioned and tested. Protecting students from unwelcome ideas is like refusing to vaccinate them against measles. When they go out into the world, they will be unprepared for its glorious but sometimes challenging diversity.

The notion that people have a right not to be offended is also pernicious. Offence is subjective. When states try to police it, they encourage people to take offence, aggravating social divisions. One of the reasons the debate about transgender rights in the West has become so poisonous is that some people are genuinely transphobic. Another is that some transgender activists accuse people who simply disagree with them of hate speech and call the cops on them. Laws criminalising “hate speech” are inevitably vague and open to abuse. This is why authoritarian regimes are adopting them so eagerly. A new Venezuelan law, for example, threatens those who promote hatred with 20 years in prison—and prosecutors use it against those who accuse ruling-party officials of corruption.

Governments should regulate speech minimally. Incitement to violence, narrowly defined, should be illegal. So should persistent harassment. Most other speech should be free. And it is up to individuals to try harder both to avoid causing needless offence, and to avoid taking it.■