We’ve got to unilaterally change the Withdrawal Agreement, insists Boris Johnson, because the EU is trying to split the UK apart. Those dastardly continentals have connived to split this great country asunder, placing a trade border down the Irish Sea. It’s unacceptable. It’s wrong. We must stop it.

A canny observer, with a memory that stretches all the way back to last December – if you can imagine such a feat – might remark that the person who negotiated, campaigned for, and won an election on this deal was… Boris Johnson. Prime Minister. “Let’s get Brexit done,” he told us, fatuously. “We’ve got an oven-ready deal,” he lied. It was only ever going to get us out of the door – and, apparently, it’s now not even good enough for that.

Across the Atlantic, let’s pick any one of the nonsensical lies Trump has told this week. How about the assertion that Joe Biden is on performance-enhancing drugs to make him appear lucid? Anyone who’s watched a couple of minutes of Biden speaking extemporaneously will conclude that he’s of perfectly sound mind, and that the Trump campaign’s claim that he has dementia is self-evidently a lie and a baseless smear. Big surprise – the man who has a stutter sometimes trips over his words.

Both of these men lie in a way that is seldom seen in western politics. Politicians evade the truth or talk around the question, yes, but an outright lie is exceedingly rare. Not so with Johnson and Trump. And this is not to equivocate between the two – Trump’s incessant lying is clearly the result of a narcissistic, sociopathic compulsion to rewrite reality, while Johnson is a more limited liar in the classical style: self-interested, nakedly ambitious, amoral. But the way they are treated is more or less the same.

Take the BBC’s current reporting of this furore:

No 10 says the Internal Market Bill was a “critical piece of legislation for the UK”.

But Mr Cameron said he had “misgivings” over it and breaking an international treaty should be the “final resort”.

Former Tory PMs Theresa May and Sir John Major, and Labour’s Tony Blair and Gordon Brown have condemned the plan.

However, Boris Johnson’s official spokesman said the bill delivered a “vital legal safety net” so the government can “take the necessary steps to ensure the integrity of UK’s internal market” – steps it hoped never to have to use.”

That style plays out in the rest of the article; essentially a he-said, she-said with no clear factual conclusion. Downing Street says one thing, but ‘critics say’ another thing. This style of reporting leaves the reader at a loss. Who is right? Both sides sound reasonable. Even the so-called analysis embedded within that article talks around the point, merely suggesting that this is important and – in a down-with-the-kids cheeky wink to the audience – acknowledges that there’s a lot of jargon floating around.

So let’s be clear: Boris Johnson is lying. He negotiated the Withdrawal Agreement and said it was a fantastic result for the UK. When he tells you that it was negotiated at pace, and that it was rushed, he thinks you’re an idiot. (Indeed, the bulk of the Withdrawal Agreement was negotiated by Theresa May – the only part that changed under Johnson’s negotiating team was the removal of the Northern Ireland backstop and the shift of that border to down the Irish Sea).

And let’s also be clear: Donald Trump is lying too. He isn’t ‘making false statements’ or ‘erroneous claims’, as US media are compelled to say (because they feel unable to ascribe intent). The right wing lied about Hillary Clinton’s health four years ago – recall the insistence that she had Parkinson’s, and that she wouldn’t even be able to finish a four-year term – and they’re lying now when they attack Biden’s health.

And here we have the legitimacy problem.

These men occupy the premier positions of power in their countries, and the news media can’t exactly ignore them. But by virtue of their position, their many lies are treated as if they might well be true. It’s artificial fairness – and by affording to both sides the potential for truth, you give succour to liars and diminish those who speak the truth. It encourages a sort of factual nihilism – if reading that BBC article gives any indication, objective truth doesn’t exist and even if it does, who cares? They’d rather their readers believe them to be scrupulously fair than to actually be fair – which, in this case, is calling a lie a lie and the truth the truth.

I don’t generally have a problem with the BBC. People who say that the corporation is biased are usually unhappy that their reporting doesn’t conform to their worldview. But I do think the BBC is frightened, and that their fear clouds their judgement. They’re constantly hammered on both sides for bias, but only one party holds the purse strings, and it’s clear that the Conservatives would demolish them in a moment if they could. The BBC don’t want to give them any rope – but by holding their fire, they paradoxically cede more ground.

Donald Trump was never fit to be President. His opening campaign statement – that Mexicans are rapists and murders – was enough to disqualify him. But because he now is President, this self-evidently unfit man has been given an undeserved level of legitimacy. Likewise, Boris Johnson – who was from the available evidence quite obviously a liar, a charlatan, and generally a nasty piece of work – was not fit to be Prime Minister, and yet whatever lies come out of Number 10 are now treated as golden nuggets of truth.

Is there an easy answer to this? No. But something must be done. Lies have served the two men on either side of the Atlantic well, and an observer could reasonably conclude that the way they comport themselves is the easiest way to win power.