So you think you're free to speak your mind? Think again. We are, all of us, increasingly bubble-wrapped in the sounds of silence.

Silencing the intelligentsia has always been totalitarianism's tool of choice. But there's only so much you can achieve with prisons and pig-farms. Now, as public intelligence shrinks to a hoarse whisper, it seems corporatised culture may succeed where more gun-pointed regimes have failed. 

Silence is the sound of no hands clapping.

The mindless din that now passes for civil debate is generally attributed to populism of one kind or another – the internet, the market, democracy itself. But perhaps that's wrong. Perhaps the silence is coming from the top.

It's not just scholars and academics, increasingly silenced by ludicrous administrative burdens, vanishing tenure, a casualising workforce and despair at the commodification of what we still call "higher" education. In a way, that's the least of it. Across journalism, politics, agriculture, medicine, law, human rights and teaching, the gags are growing in size, number and efficacy.

Watching the film Citizenfour, I was struck not only by Edward Snowden's lucid courage but by his misplaced confidence in the rest of us. Seeing his own disclosure as merely the first brick from a Berlin wall of silence, Snowden was touchingly certain that, once his bit was done, we'd all follow. We'd all take our stones of silence and chuck them at the jackbooted armies of spin, smugness and compliance.

How wrong he was. We watched in silence, seeing Snowden, Assange and poor little Bradley Manning as a race apart: heroic figures to be admired, but not emulated. Even the term "whistle-blowers" sets them apart, carrying with it our heartfelt hope not to be similarly called.

But they're not apart. They are all of us. Consider journalism. The sacking of SBS journo Scott McIntyre for his Anzac Day tweets was shocking on several fronts. First, I was shocked that Malcolm Turnbull – who first came to intellectual prominence for defending ex-spy Peter Wright's right to tell the truth – had so thoroughly changed sides.

Second, I was shocked that SBS would act on Turnbull's "offensive" tag. Third, that anyone in this country, but especially a journalist, could be sacked for voicing political opinion.

I was also shocked by the hypocrisy. It was SBS' own, very fine series The Great Australian Race Riot by Sally Aitken and Peter FitzSimons, that detailed just how racist and violent the World War I diggers were. Armed with guns, bayonets and flesh-shredding Gallipoli-originated 'jam-tin bombs', they formed thousands-strong vigilante mobs in Brisbane (1919), Broome (1920) and Kalgoorlie (1934) to "defend" loyal royal white Australia from the Russians, the Japanese and the Italian-Slavic communities, in Kalgoorlie burning 117 homes.

But most shocking of all was the casual response of others to my dismay. "Well duh," was typical. "Everyone has a social media clause. You try saying something offensive, see how you get on."

It's true. Professionals of all kinds now expect to be governed by social media clauses that specifically fetter their public opinions and sometimes even require public positive comment.

This is terrifying. It's like your boss has the right to advertise on your house – only worse, because it's inside your head. It is thought-police territory and its ultimate effect is blanket self-censorship, where the threat barely needs to be explicit because an entire generation of young professionals has internalised its norms and accepted its dictates.

And even that's just the tip of it. There's the government's tireless bullying of Human Rights Commissioner Gillian Triggs for her staunch public defence of both asylum seeker rights and the rule of law, pretending that she's the one playing politics, although both roles fall within her job as commissioner and her duty as a citizen.

There's the truly sinister Border Force Act. Slipping unseen through parliament last month, it threatens doctors, teachers and other contractors assisting detained asylum seekers with two years' jail if they speak publicly about conditions there.

As the government rhythmically repeats, the innocent have nothing the fear from scrutiny. So what exactly on Manus and Nauru are they are so desperate to hide? Are the tales of children being passed around "like packets of cigarettes" actually true?

There's also the "ag gag" legislation currently before Senate. Disguised as an "Animal Protection" amendment to the Criminal Code, this bill is in fact designed to intimidate protesters. It gives individuals who record anything they regard as animal cruelty one day to report it – regardless of whether the cruelty is real or the law known to the person – or face a $5100 fine. This can only exacerbate the animals' plight.  

There's the huge, 12-nation Trans-Pacific Partnership agreement, so powerful it will let US tobacco corporations sue Australia for loss of "expected future profits" from plain packaging rules, but so secret even our governments can't tell us about it, and we know this only via Wikileaks.

And there's the application of this same knee-jerk secrecy to city-making, where even with ultra-public buildings like the Opera House, treat the public as the enemy – as in the cloak-and-dagger design competition for a Visitors Centre on the forecourt, where none of the schemes, including the winner (by Rachel Neeson) were ever made public.

None of this is legitimate. It's not commercial-in-confidence. It is rule-by-ignorance, and in excluding from public debate everyone of knowledge, insight or learning it turns democracy into an emotive bloodbath run by spin-merchants and rabble-rousers.

It's as though we have all tacitly accepted the government's view that "the media" is a bad and scary domain, where be dragons. Say what you will in private, but speak not your mind in public, ye citizens, for fear of – what? Enriching the democratic debate? Improving government? Making political progress? Heaven forbid.

We can't afford this. We need democracy to work with intelligence and rich collective imagination. To speak freely in public is not just a right; it is a duty that should be constitutionally enshrined. Contractual gags should be banned. Silence is the sound of no hands clapping.

The sound of silence stifles our freedom