Long after he leaves office — for prison, Moscow, a six-month residency at Caesars Palace, wherever — the lies and tantrums that define Donald Trump's Twitter feed will keep historians and psychologists scrambling to make sense of it all. The fiasco known as Sharpiegate is just the latest example of social media amplifying his grotesque instability. But of all the filth he has foisted on the world since he first learned to stab at his phone with his tiny thumbs, one tweet in particular remains the most resonant emblem of Trump's cynicism and his recklessness.

On 22 November 2015, more than a year before he turned the West Wing into a crash pad for fringe-right mediocrities, Trump re-tweeted an image expressly designed to get the shriveled hearts of white supremacists racing.

Beneath a banner titled "USA Crime Statistics: 2015," the image in question features a masked, dark-skinned figure brandishing a handgun. The accompanying stats, sourced by the "Crime Statistics Bureau — San Francisco," are striking:

"Blacks killed by whites — 2%"

"Blacks killed by police — 1%"

"Whites killed by police — 3%"

"Whites killed by whites — 16%"

"Whites killed by blacks — 81%"

"Blacks killed by blacks — 97%"

Some readers might already be scratching their heads. What is the "crime statistics bureau"? Why is it located in San Francisco? Is it a state agency? Federal? (Spoiler: It doesn't exist.)

OK, forget the bureau. Let's look at the numbers.

How is it that both the "Blacks killed by …" and "Whites killed by …" percentages add up to exactly 100 per cent? Did all of America's enterprising Asian, Hispanic, and mixed-race killers take that year off? Did every deadly instance of crime in the US in 2015 involve only white people, black people, and/or cops?

Only 16 percent of white people killed in 2015 were killed by other Caucasians? And 97 per cent of black people were killed by other African Americans?

If those statistics seem a bit sketchy, it's because they are. In fact, no matter how you read or interpret them, they're way, way off.

But the numbers aren't just wrong; they are wrong with intent. They are meant to frighten white people or, better yet, reinforce the assumptions of those who long ago bought into our founding lie: that African Americans are inherently violent and pose a constant threat to pale, god-fearing folk.

Take just some of the tweet's craziest assertions — for example, that 81 per cent of whites murdered in 2015 were "killed by blacks." The problem with that? According to the FBI, in 2015 more than 80 per cent of white homicide victims were killed by other white offenders; about 15 per cent were killed by black offenders.

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And how about the 2 per cent of "blacks killed by whites"? In truth, FBI data indicate that number was closer to 10 per cent.

We could go on, but ultimately the specific numbers in Trump's tweet don't matter. What does matter is that a major-party candidate for president of the United States re-tweeted a racist load of crap from a suspicious, seemingly neo-Nazi Twitter stream — and 10,000-plus followers "liked" it.

There's no telling who originally created the crime data image, either — the account from which Trump re-tweeted this corrosive BS, @CheesedBrit, was deleted long ago.

But that, too, is beside the point. The core takeaway here is how a single, four-year-old tweet perfectly distills Trump's lifelong contempt for the truth, his intellectual shabbiness (would anyone with a room-temperature IQ readily accept data from the "Crime Statistics Bureau"?), and the breadth of his casual bigotry.

And honestly, who among us could possibly be surprised? From the infamous full-page newspaper ads he bought in 1989 calling for the execution of the "Central Park Five" — all of whom were eventually exonerated, of course — to his role as the loudest and most obnoxious of the hate-fueled Birthers, Trump has long gibbered in racist code. Today, he stokes white resentment at his spasmodic rallies with one aim: to accrue more power and build his own wealth.

Inflammatory, semi-coherent rhetoric, online and off, is Trump's trademark. But his personal attacks on American heroes, his brown-nosing of enemy dictators, his deranged lies (watch out, Alabama!) — none of these behaviors more succinctly captures who and what Donald Trump truly is than one self-serving, patently racist image he casually spewed into the Twittersphere four long, long years ago.