Last week, Jessica Ennis-Hill took the brave step of saying she would have her name removed from a stand at Bramall Lane if Sheffield United re-signed convicted rapist Ched Evans. The inevitable consequence was a blurt of rape threats from members of Evans’ fanbase. One prize specimen, @RickieLambert07, replied to criticism by saying: “Freedom of speech mate… I’ll say what I want when I want!” I cannot say for sure that @RickieLambert07 isn’t a lawyer but he certainly has a shaky grasp of Article 10 of the Human Rights Act.

If you believe in freedom of expression you often find yourself in terrible company. Right now, misogynists are enjoying a Voltaire moment, having been robbed of the comedic stylings of Dapper Laughs and, if the campaign to deny him a UK visa succeeds, the sinister “dating advice” of repulsive Californian pick-up artist Julien Blanc. It’s fortunate that the penitent Daniel O’Reilly chose to become The Artist Formerly Known as Dapper Laughs, the Ziggy Stardust of bantz, rather than a lad martyr, but I worry that Blanc will turn a state ban to his advantage.

As a teenager, I first encountered censorship as a tool of the religious right. This was the era of Martin Scorsese’s The Last Temptation of Christ, Andres Serrano’s Piss Christ and Body Count’s Cop Killer, not to mention The Satanic Verses. In each case, I saw the would-be censors as intolerant, ignorant and absurd. For one thing, many of them had only a sketchy apprehension of what it was they were trying to ban, learning about the offence second-hand. Second, they made the mistake of thinking that the artwork was a cause rather than a symptom, as if, absent Body Count’s rap-metal provocations, African-Americans would have felt warmly towards the LAPD. Third, the outrage tended to have the effect of publicising and ennobling the offending work. All of this was sharply satirised by the Father Ted episode in which Ted and Dougal’s muddled protest against a “blasphemous” movie (“Down with this sort of thing”) ended up making it a smash hit.

I was naive to think that censorship, in its many forms, was restricted to the right wing but the effect of reading about these debates at an impressionable age was to give me an enduring suspicion of bans, wherever they come from. I felt the same reservations when, in September, the Barbican bowed to pressure to cancel Exhibit B, South African artist Brett Bailey’s installation about racism. Responsibility ultimately lay with the Barbican but the protesters’ aim, spelled out in a Change.org petition, was always cancellation of a “racist” exhibition that they hadn’t actually seen. Consequently, nobody was allowed to find out if it was as crass and misguided as they claimed. In a prepared statement, Bailey’s black performers said: “We welcome protest, but surely it’s best to have as much information beforehand, so your opinion is truly informed ... And surely your right to protest should not impact another person’s freedom of thought and speech.”

Protesters outside the Barbican call for a boycott of Exhibit B, by South African artist Brett Bailey. Photograph: Thabo Jaiyesimi/Thabo Jaiyesimi/Demotix/Corbis

The fact that some people I usually agree with welcomed the Barbican’s cave-in shocked me. It’s illogical to condemn the Metropolitan Opera’s cancellation of a live transmission of John Adams’ opera The Death of Klinghoffer (the Met somehow deemed it “not antisemitic” yet “inappropriate at this time of rising antisemitism”) while applauding the closure of Exhibit B. If you oppose censorship then whether or not you like the thing being censored is irrelevant. In fact, the principle is only tested when you loathe the thing being censored (providing, of course, you have seen it).

That’s basic stuff, almost too obvious to spell out, but draconian censorship is becoming an increasingly common tactic among people who consider themselves liberals, from Exhibit B to the mission creep of refusing controversial speakers a platform at universities. Freedom of expression always has exceptions, for example legally proscribed hate speech, but allow too many and it suffers death by a thousand cuts. While many ideas are offensive, only a few should be deemed so unacceptable that they can’t be heard.

I suspect the blurring of that line is related to the fever pitch of online discourse. The internet is so perpetually cross that it’s increasingly hard to make an impact with mere disapproval. In the outrage arms race, it’s tempting to go straight for the nuclear option. When Asian-American activist Suey Park was offended by a satirical skit on The Colbert Report in March, she started the hashtag #CancelColbert, despite neither wanting nor expecting the show to be cancelled. “#CancelColbert was never literal, but it was a way to say, ‘Hey, improve Colbert,’ knowing that trying to improve Colbert would never trend, knowing that it would never get heard,” she told Salon.

At least Park was honest, although it’s unclear how many people who joined the hashtag realised that it was calculated hyperbole. The other week supporters of #DropDunham, who wanted Planned Parenthood to sever ties with Lena Dunham over one passage in her memoir, seemed entirely sincere. The distance between “I hate this” and “This must be stopped” can be invisibly narrow.

Rather noise than silence. Allowing Exhibit B to go ahead in other countries didn’t muzzle demonstrators or quash debate there. Similarly, I’d rather see protestors expose the wretchedness of Julien Blanc on the ground (as if he needs any help) than grant him the outlaw glamour of an enemy of the state. Silencing people you hate can be an alluring short-term goal, a symbolic victory against the prejudices that they embody, but it has long-term risks. If you poke too many holes in the fabric of freedom of expression, then you cannot complain when the bigots, authoritarians and fanatics pour through them.