I have a problem – what is now called ‘an issue’ – with freedom of speech. I have never been able to accept what all right-on readers of the Guardian take for granted: that it must be absolute. It is a pity, for example, that the repellent Glaswegian, Frankie Boyle, gets away with his ‘jokes’ about ill and disabled people (though how satisfying that he has been exposed out of his own mouth in the new film about poor Amy Winehouse).

Even the Guardian, despite its protestations to the contrary, is not an unqualified believer. You bet that its editor rejects pieces which depart in some way from the required orthodoxy. In my own experience with this little magazine over the last 20 years, my repression of freedom of speech always leads to trouble with the wounded contributors. One told me to ‘**** off, Kenneth'; another didn’t speak to me again for 10 years. Not all the rejected pieces were misogynist, homophobic or religiously bigoted; some just weren’t very good. But I am always conscious that these editorial decisions inhibit in a small way the apparently inalienable right to free speech. It would be hypocritical to pretend otherwise.

Conversely, when I think I am encouraging freedom of expression, and taking a certain professional pride in doing so, that can lead to trouble too. Bigger trouble, usually. Here is a tiny example of what I mean. One November week in 2002, some of the most powerful and/or influential people in Scottish public life – about two dozen of them – drew up at a hotel in the Gorbals ill-prepared for the grilling they were about to receive from the young delegates to a conference I was organising.

At the first session, James (Beta-blocker) Black and Ian Hamilton QC were treated with respect, maybe also a little deference, but after that it was no-holds-barred. They managed to extract from the then first minister, Jack McConnell, an admission that he was a socialist. A socialist in Tony Blair’s Labour Party? Heck. That made headlines the next morning. Roseanna Cunningham, the nationalist tribune for Perth, claimed one evening that there was not a problem of homelessness in her town, only to be corrected by two young people who happened to be homeless in Perth. Nobody got away with anything that week. It was glorious. It was free speech at its challenging best.

Not everybody enjoyed the experience. The distinguished Free Kirk theologian, Donald Macleod, whose writing I had always admired, was invited to discuss deep questions of faith. It was an uncomfortable session. The young people poked and prodded, though not in any personally objectionable way (or so I thought), but by the end the speaker was hot under the dog collar. (Not that he was wearing a dog collar. Rather a smart suit, I seem to remember.) He made it clear to me as soon as it was over that he had been humiliated, suggesting that I should have intervened in some way. He then stormed out of the hotel. It was an impressive sight.

We have not spoken since. That’s freedom of expression for you. But I was more than a little intrigued by the recent discovery that my old friend Brian Wilson, founder of the West Highland Free Press, had gone to the barricades for the same Donald Macleod over an article the latter had written about the possibility that our ‘friendly Muslim shopkeepers’ might soon feel compelled to march behind the Islamist fundies. Apart from the condescending reference to Muslim shopkeepers, there wasn’t much wrong with the piece – another expression of free speech; there’s a lot of it about – which nevertheless prompted the constructive dismissal of the distinguished Free Kirk theologian and the subsequent firing of Brian Wilson.

Would I have gone to the barricades for Professor Macleod? Maybe not. The person I felt sorry for was Brian Wilson, who created the best newspaper to have been set up in Scotland in my lifetime and has suffered the fate of so many creators.

Just as I was contemplating in a detached way the many difficulties of defending, or failing to defend, free speech, I was faced with a case closer to home. Jill Stephenson, former professor of German history at Edinburgh University, had been a valued contributor to the Scottish Review, mostly on education, though more recently – as recently as the July edition – on her experiences as a hospital patient. During the referendum campaign she was an effective campaigner for the No side. Since then she has continued to use social media to propagade the unionist cause or attack the nationalist one.

But then Professor Stephenson went too far: she sent out a Tweet describing Mhairi Black, the young SNP MP, as an appalling harridan and a foul-mouthed little slut. There was no justification for either of these potentially actionable slurs and the language was in any case deplorable. I emailed the professor to express shock and disapproval, suggesting that she should apologise. I don’t know if she ever did, but I doubt it. She has put it on record that she doesn’t give a flying **** – I’ve censored that bit of free speech too – what her critics think. A few days later, her folly was exposed by Mhairi Black’s thoughtful and dignified maiden speech, which has earned widespread admiration.

I might as well repeat another thing I said to Jill Stephenson: that if Scotland is to be characterised by this level of abuse on both sides of the constitutional question then I fear for my country and despair of its future. Would I defend to the death the right of these people to say what they want to say, no matter how foul? I wouldn’t. There are limits. And the sooner we start respecting and observing them in a spirit of decent self-regulation, the sooner we will protect freedom of speech from the next big thing: a bad beast known as state censorship.