On 26 August, I spoke at the University of Sydney on PC, free speech and campus life. Here are my opening remarks.

Ladies, gentlemen, people of indeterminate gender.

There are two reasons you should be freaked out by political correctness.

The first is that it prevents people from saying what they want to say, from expressing what they believe to be true. And it is fundamentally illiberal to stop people from expressing their beliefs and their ideas.

And the second is that it prevents the rest of us from hearing those ideas and deciding for ourselves if they are good or bad. It infantilises all of us through denying us the right to weigh things up, to argue over them, to be the arbiters of what is right and what is wrong.

Instead it gives that role to a dictatorship of do-gooders, who decide on our behalf what words and thoughts are fit for public consumption.

On the first point, the stifling of non-mainstream thought. One of the great fallacies of PC is that it’s just about being polite. They call it “institutionalised politeness”. It’s about eradicating ugly terms and ethnic slurs, so what’s the beef? Who could be against that, except racists and misogynists?

This is disingenuous in the extreme. PC doesn’t only prevent the use of shocking words; it strangles the expression of ideas, ideologies, moral beliefs, and religious convictions. Like every form of censorship in history, it curtails the expression of beliefs that an elitist group of people have judged to be wicked or foul.

Let me give you some examples of campus clampdowns on un-PC speech which are actually assaults on the expression of moral convictions.

At a university in America, a newspaper has said it will no longer accept op-eds opposed to gay marriage, criticism of gay marriage being the latest verboten utterance of our unforgiving age. It dresses this up as a PC measure to protect gays from offence, but the real consequence is that Christian beliefs, traditionalist convictions, are no longer permitted.

On some campuses in Britain, criticism of the Muslim veil is now branded “Islamophobia”, or even “hijabphobia”, and you will be shushed or shamed for doing it. This is done in the name of protecting Muslim women from offence, but the impact is to demonise an utterly legitimate moral viewpoint: that the veil is not a great thing.

On campuses across the West, including this one, any expression of support for Israel is met with a furious response. Student radicals are like Pavlov’s dogs when it comes to Israel: any mention of Zionism and they go mental. They ban or boycott all things Zionist, in the same way far-right regimes once banned or boycotted all things Jewish.

And they try to disguise this ugly intolerance in PC language, as an attempt to prevent the expression of offensive words that might pollute campus life and harm Muslim students in particular; apparently pro-Zionist commentary makes students feel “unsafe”. But once again, it is fundamentally a political idea, the idea that Israel is a legitimate entity, which is being crushed here, not just un-PC words.

So don’t buy the idea that PC is merely politeness or good manners. It’s about policing the parameters of acceptable thought. It’s about patrolling the borders of what it is acceptable to think and express.

Whether campus censors are raging against gay-marriage sceptics, or climate-change deniers, or people who think Israel is a cool country, they’re seeking to restrict the public expression of moral views.

Especially contrarian views. As we saw with the mob at the University of Western Australia that shut down Bjorn Lomborg’s climate-change institute on the basis that Lomborg is a “climate contrarian”. Perhaps all academics should in future be asked: “Are you now or have you ever been a climate contrarian?” How extraordinary that those who claim to be left-wing, once the home of contrarian thinking, should now treat contrarianism as tantamount to a crime, to be screamed and chased off campus.

And the way they stymie all these non-mainstream, supposedly controversial ideas is by branding them offensive, “hate speech”. What they forget, because they really are this arrogant, is that one person’s “hate speech” is another person’s deeply held moral conviction.

The Christian student who thinks marriage should be between a man and a woman truly believes that. The Jewish student who thinks Israel is a great country really believes that. And to my mind, stopping people from expressing things they truly believe is outrageous, an unspeakable offence against democracy, especially at a university, where ideas are meant to flow and crash and battle it out.

Those students believe those things just as surely as PC students believe the ABC is wonderful or Julia Gillard was a good prime minister. Those are mad ideas with little basis in fact, but you aren’t prevented from expressing them, are you? Imagine if you were. Well, now you know exactly how the un-PC people feel, who are harassed or “no platformed” or prevented from holding meetings for saying what they believe in their heart of hearts to be true and right.

And the second point about PC: it doesn’t only ride roughshod over the rights of the speaker; it denigrates the rights of the audience, too.

The reason the PC think certain ideas and words shouldn’t be expressed is because they don’t trust you. They think if a far-right speaker comes to campus, all you brainless idiots will be transformed into violent racists. They think if you hear the Christian viewpoint on marriage, you will become demented homophobics. They want to restrict public speech because they see you as fickle morons; as psychos-in-waiting who must be kept non-psychopathic through censorship, through the hiding-away of naughty words or images that might turn you mad.

Even worse, they see some of you as fragile victims, who need protection. The PC consider themselves the great protectors of minorities from offence. They want to save black people from racist words, gay people from Christian beliefs, women from gruff male banter.

How paternalistic. How insulting. The idea that we need these wise, white, impeccably middle-class student leaders to protect blacks and others from harmful speech is not a progressive one. It is neo-colonialist. It is shot through with a white-saviour complex and a view of minorities as incapable of negotiating public life on their own.

This is why you must oppose PC. It silences people; it infantilises everyone; and it allows tiny groups to style themselves as the guardians of moral decency and defenders of the poor, sad little people. PC should be burnt to the ground. Go forth and be as un-PC as it’s possible to be.

These were my opening remarks at the University of Sydney on 26 August 2015.