In a recent review of Volker Ullrich’s new biography of Adolf Hitler, “Ascent 1889-1939”, the Pulitzer Prize-winning critic Michiko Kakutani clearly had in mind contemporary events.

Noting that the dictator had gone from being regarded as a self-obsessed “clown” with a strangely “scattershot, impulsive style” to “lord and master” of the German Reich, Kakutani never actually compared Hitler’s rise with that of Donald Trump.

But in his piece for the New York Times, he went on to highlight Hitler’s loose relationship with the truth, his promise “to lead Germany to a new era of national greatness”, repetition of “manta-like phrases” at large rallies, and the fateful tendency of opponents to underestimate him.

So Kakutani’s point was implicit, and indeed I’ve been struck by some of the same parallels as I devour Ullrich’s authoritative tome. At the same time, it’s important not to get carried away; it seems unlikely that Trump is gearing up to abolish the Democratic Party, tear up the US constitution and ban the free press.

Over the past few weeks, however, some have eschewed Kakutani’s subtle approach and directly denounced the president-elect as an out and out fascist. But while this is tempting – and in some respects justified – I don’t think it’s altogether helpful. Not only is it an inadequate strategy, but it’s factually incorrect.

“Fascism”, at least the early 20th-century European variety, held that liberal democracy was obsolete, and that the mobilisation of society under a totalitarian one-party state was necessary to restore national “greatness” and combat economic decline. Italy, Germany and Spain all fitted this definition.

This, then, is the crucial distinction: however objectionable Donald Trump is, he is nevertheless operating within the limitations of both the law and a democratic system of government, however flawed that might be, while the institutions and economy of the US are immeasurably stronger than those in inter-war Europe.

Such context was dispensed with in a discussion on BBC Radio Scotland’s “Shereen” programme on Saturday morning, the writer and actor Sergio Casci calling Trump “a fascist with a small ‘f’ who’s just become president”. That lower-case qualification aside, he also said that we should stop “worrying” about the language used to describe the President-elect and alt-right.

That I cannot accept, for language is incredibly important, and simply dispensing with the rules because the other side have already done so is not a very compelling argument. By contrast, earlier in the discussion Casci had hailed Fidel Castro as a “hero of the 21st century” and explained away his regime’s considerable human rights abuses on the questionable basis that Cuba had been at “war” with the United States.

So just to clarify, according to this world view Castro, who was responsible for the death or torture of tens of thousands of people, is considered more palatable than Donald Trump, who however extreme rhetorically hasn’t (yet) done any physical harm. Presumably Casci would have rejected Marco Rubio’s description of the former Cuban leader as an “evil, murderous dictator who inflicted misery and suffering”, but it happens to be empirically more accurate than calling the 45th president a “fascist”.

Since Castro’s death, meanwhile, some of those on the Left haven’t covered themselves in glory, from Canadian Prime Minister Justin Trudeau’s qualification-free tribute to Jeremy Corbyn calling him a “champion of social justice”. Only Liberal Democrat leader Tim Farron got it broadly correct, calling Castro a “vastly significant” leader (true) responsible for “appalling human rights abuses and brutal summary executions” (also true). But for many on the Left, as long as you call yourself a “socialist” and resist imperialism, then all is forgiven.

Doubtless this will leave me open to another simplistic notion currently doing the rounds, that rejecting terms like “fascist” in the context of US politics is somehow “normalising” Trump and his followers. Ullrich pre-empts a similar critique in the introduction to his Hitler biography, arguing that his “normalised” account doesn’t make his subject any more “normal”, but actually “even more horrific”.

To repeat, it’s important to keep these things in perspective, particularly as terms like “alt-right” and “fascist” dominate political discourse in the US and Europe to an astonishing degree. In the past week alone a group of alt-righters gave Nazi salutes and shouted “Hail Trump” at an event in Washington DC (something Trump was content to “disavow and condemn” last week), while in the UK Thomas Mair was imprisoned for the murder of MP Jo Cox.

How to categorise Mair, with his collection of Nazi tomes? A victim of mental health issues or calculating politically-motivated killer? The counter-extremism think-tank Quilliam Foundation made the perceptive point that many were reluctant to call him a “terrorist” in the same way they had Lee Rigby’s killers because terror attacks are more easily associated with young male Muslims than middle-aged white men. Again, language is not only important but revealing.

Part of the problem is that the term “fascist” has been devalued by decades of casual and erroneous usage. Every US or UK political leader since Reagan and Thatcher has generally been denounced by the Left as a “fascist”, often by the same people who wouldn’t dream of describing Castro or Vladimir Putin as a “dictator”.

Thus “fascist” has become more a term of abuse than a sparingly-wielded adjective. Years ago I remember watching the left-wing comedian Jeremy Hardy deal with hecklers by yelling “fascist!”, but that was the point: he was making a self-aware joke about the word’s use to close down debate rather than engage.

Both Labour and SNP types have been guilty of this. I remember back in May 2007 the former Labour MP Anne Moffat telling the House of Commons that “proportional representation gave Germany Adolf Hitler and in Scotland to a lesser degree we’ve had the member for Banff and Buchan”, a gratuitously absurd reference to Alex Salmond’s recent formation of a minority government.

And just last week, the SNP’s digital strategist Ross Colquhoun, who seems to spend more time generating unhelpful news stories than he does helpful strategies, suggested in a series of late-night tweets that Unionists and Tories were “embracing fascism for political gain”. Colquhoun, of course, didn’t consider his own party leader writing to congratulate Trump or Alex Salmond saying he should be “given a chance” as “embracing” fascism.

Thus terms like “fascist” or “fascism” have become devoid of all meaning or impact, much like “social democracy” and “social justice” from another ideological direction. Of course this doesn’t mean indulging newly-confident political movements: “alt-right” is a deliberately fluffier term than “Nazi”, but “neo-Nazi” or “neo-fascist” would be steps in the right lexicological direction.

Those in public life ought to be reluctant to use terms like “fascist” or “dictator” loosely, for they’re the most powerful epithets in the political lexicon and the English language is rich enough to accommodate alternatives.