The left-wing “journalist” and professional agitator Marc Wadsworth has struck the first blow against the new mayor of London, Boris Johnson – and has done so on territory upon which Boris felt himself, perhaps rightly, to be vulnerable.

Wadsworth interviewed Johnson’s senior political adviser, James McGrath, for a blog read by almost nobody (The-Latest.com). Why McGrath bothered to talk to the man – over a nice cup of coffee – may remain for ever a mystery.

Anyway, Wadsworth recorded their conversation and then wrote it up, revealing to his handful of readers the shocking racism at the core of Johnson’s new regime. Wadsworth himself pronounced it “breathtaking”; others have suggested that it called to mind the “language of the BNP”. Within 48 hours, McGrath was sacked.

What precisely happened was this: during the course of their conversation, Wadsworth quoted the unsubstantiated and frankly risible comments of a more prominent black journalist and supporter of Ken Living-stone, Darcus Howe, who had said that with Boris as mayor of London many black Londoners might decide to return to the Caribbean. What do you have to say to that, Wadsworth inquired. McGrath, in exasperation and some irritation, replied: “Well, let them go if they don’t like it here.”

That’s the “breathtaking” stuff to which Wadsworth alluded – although he also claimed that McGrath’s last riposte to him was “politically incorrect” and thus presumably “breathtaking” too.

McGrath had said to Wadsworth: “I know where you are on the radar, sunshine,” having suffered a series of extremely partisan questions. I assume it’s the word “sunshine” to which Wadsworth objected, although it seems to me one of the milder epithets one might throw at Marc Wadsworth. Whatever, within a very short space of time indeed, McGrath was out of a job, for having divested himself of a “racist” comment.

And here’s the justification for the sacking: one commentator, Sunny Hundal, said that telling black people to clear off “has deep associations with BNP language and terminology”. Another said: “We have heard similar comments from racists.” So in fact nobody suggested that McGrath had been racist – he clearly hadn’t – merely that racists had said the same sort of thing in the past. So now you can be done not for being racist per se, but for saying things that aren’t actually racist but that people who are known to be racist might have said. Bizarre.

Johnson still sacked him, in what the Tory blogger Iain Dale called a “despicable and cowardly” act. Clearly, the mayor took advice from the party leader, David Cameron, and it would seem even more detailed advice from the Conservative head spin doctor, Andy Coulson. Either way, McGrath is out of a job, which is a personal tragedy for him and, more to the point, a worry for the rest of us.

There is nothing in what McGrath said that could possibly be construed as racist unless you were hellbent on seeing it that way, to the occlusion of all recourse to semantics, grammar and syntax. Clearly he meant that people, regardless of their ethnic origin, who had no wish to stay in London while Johnson was mayor could clear off.

A bit brusque, maybe, but in what possible sense is it racist? Indeed, both Cameron and Johnson accepted that he hadn’t been “racist” – in which case, why sack the man? McGrath, incidentally, is an immigrant himself – an Australian, as it happens. Or, as was often reported last week, a “nononsense” Australian . . . as Australians always are. Now there’s a racist stereotype for you. James McGrath, Aussie: speaks his mind, likes a few tinnies and an agreeable Sheila, a nononsense bloke.

Both Cameron and Johnson have form, of course, albeit different sorts of form – heads and tails form, in a way. Long before he stood for mayor, Johnson wrote these words about a forthcoming trip to Africa by Tony Blair, then prime minister: “The tribal warriors will all break out in watermelon smiles to see the big white chief”, and there was the famous reference to “flag-waving piccaninnies”.

It was satire, of course, and very funny too – but you would bet against the likes of Marc Wadsworth accepting it as such. He would be less likely to break out in a watermelon smile than to howl at the moon: “Raaacissst!” And Wadsworth would have more of a point, you might argue, than he did when ruining the career of James McGrath.

On the other side of the coin, Cameron has expended some considerable energy sacking people for saying things that aren’t remotely racist but might possibly be construed as such by the likes of Wadsworth. Two obvious and fairly recent examples spring to mind.

Nigel Hastilow, a prospective candidate from the West Midlands, wrote: “When you ask people in the Black Country what the single biggest problem facing the country is, most say immigration . . . many insist that Enoch Powell was right.” Sacked – for reporting what his constituents said to him, all of which was in line with both Conservative policy and indeed the latest opinion polls, which cited immigration as the most important issue facing the country.

Some time before Hastilow’s defenestration, there was the case of Patrick Mercer, the party’s frontbench spokesman on homeland security, and his comments about life in the army – of which he knew a great deal, having departed from the Sherwood Foresters in the rank of lieutenant-colonel, been mentioned in dispatches, that sort of thing.

Mercer had said of the rough and tumble of army life: “If someone is slow on the assault course, you’d get people shouting: ‘Come on, you fat bastard’, ‘Come on, you ginger bastard’, ‘Come on, you black bastard’.” Mercer opined that all these insults were examples of bullying that should be stamped out. Nonetheless, he was sacked from his frontbench post. Sacked, incredibly, for pointing out incidents of racism and saying they were wrong.

There are plenty who would argue that politically – rather than morally or logically – this tough line from Cameron, the no-tolerance business, is quite correct if the party is to be seen as sufficiently disciplined to govern the country.

Leaving aside the morality and logic for a moment – sacking people for comments that everyone, including Cameron, agrees are not remotely racist – it is another example of the stifling of free, plain speaking and, by extension, plain thinking.

It means that whenever a politician is required to address an issue that has specific relevance to one or another of our ethnic minorities – gun crime, educational underachievement, immigration, minority religions, terrorism – he or she will do so very gingerly, if at all.

The problem will be skirted around and more often than not left unsaid. Better to let the problem fester than run the risk of being stitched up likea kipper by some opportunist like Wadsworth and then being peremptorily removed from your post.

One reason it has become easier for the ovine bleat of “raaaccisst” to be issued right, left and centre is the much broader definition of the term, as introduced by the government.

The police are now required to treat any criminal matter that the victim claims was racially motivated as being racially motivated, full stop. Even if it palpably isn’t. If the “victim” says it’s racist, then it is racist, and there’s an end to it.

Pretty much every ill that befalls someone could conceivably be put down to racism. And this institutionalising of victimhood, this über-sensitivity, has crept into our political discourse and our culture in general, despite the suspicion that the vast majority of our ethnic minority citizens find the whole thing invidious and insulting.

If there is hope, then it may come, oddly enough, from the Equality and Human Rights Commission. Its boss, Trevor Phillips, professes himself sick and tired of these endless, corrosive debates about what is supposedly racist and what isn’t.

“We want people to be allowed to speak freely,” he told me, although he would not be drawn on the instances mentioned above. “You should be okay to say anything you like so long as it’s not calculated to offend.”

The commission is holding a seminar next month on race and language, in an attempt to arrive at some sort of consensus on the matter. Normally, if a quango met to discuss what sort of language we should all be allowed to use, one would treat it with intense suspicion, if not outright hostility; but I fancy that Phillips and co are probably rather more on the side of liberty and freedom of speech than Conservative Central Office.

Maybe James McGrath should wander along and offer his tuppence-worth. Certainly he has no intention of retracting his “breathtaking” response to Wadsworth, because he doesn’t think that what he said was wrong in any way.

In a neatly ironic twist, given his comments to Wadsworth, it was McGrath who actually left the country as soon as he was relieved of his post, although one hopes he’ll be back.

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