No intelligent person should be tempted by "All lives matter," the insidious slogan that's increasingly fashionable in conservative circles.

Not that it isn't true. Its self-evident banality is actually its power. How can anyone argue with such a sentiment?

But let's be clear: the slogan was specifically designed as a political weapon to neutralize Black Lives Matter, an angry, noisy movement that is beginning to frighten the mostly non-black people who possess power in the U.S. and Canada, and their uniformed enforcers.

As it should.

Consider that just this week, the mayor of Chicago fired his police chief, who, for more than a year, had refused to make public the dash-cam video of one of his officers shooting 16 rounds into a young black teenager, Laquan McDonald.

The uniformed shooter has now been charged with murder.

Take a look at the video if you need any convincing that there is a need for the Black Lives Matter movement.

Police officer Jason Van Dyke charged with killing Laquan McDonald 0:24

McDonald, 17, was walking jauntily along under streetlights, after having used a knife to vandalize the tire of a police cruiser.

There is no audio, but all the reports have said he wasn't showing the absolute deference demanded by the white police who were pointing their weapons at him from a few metres away.

Suddenly, one of them fires, and McDonald collapses. The officer then unloads 15 more rounds into his body, emptying his clip. You can see the corpse jerk as the rounds hit; each creates a puff of dust.

Here's the video

No wonder the police chief didn't want anyone seeing the video while the shooting was being investigated.

Had it not been for the determined protests of the Black Lives Matter people, though, this "matter" might have been dealt with internally, ending with a bland written statement that the shooting was justified, as has been the case so often in the past.

Of course, the policeman charged with murdering McDonald may yet be found not guilty, if history is any guide.

Just last year, a grand jury declined even to indict a white New York policeman who leapt onto Eric Garner, an obese black man who'd been committing the crime of selling loose cigarettes in public, and choked him to death after he noisily resisted orders to submit.

There's video of that episode, too.

A man at a Black Lives Matter protest in Minneapolis last week warns demonstrators about being shot at. Four men, three white, one Asian, have since been charged with firing on BLM demonstrators, injuring five, who were camped out in a weeks-long protest in front of the police station. (Jeff Wheeler/Star Tribune/Associated Press)

Earlier this year, a jury in South Carolina did indict Michael Slager, the white policeman who gunned down Walter Scott, an unarmed man who tried to run away after a traffic stop, probably because he was behind in his alimony payments.

Slager then cuffed Scott's dead body and appeared to plant a weapon on him, evidently unaware he was being recorded by a bystander.

Again, Walter Scott was not a white man. Had he been, you have to suspect he wouldn't be dead. Here's the video.

The list goes on.

Trayvon's legacy

The killing of unarmed Michael Brown in Missouri in 2014. That was a less cut-and-dried case, and federal authorities declined to charge the policeman involved.

But it triggered prolonged rioting in Ferguson, Mo., by a black majority sick of its chronic mistreatment at the hands of a nearly all-white police force and awoke similar sentiment among blacks across America.

Then there was the event that practically restarted the American civil rights movement: the killing, in February 2012, of 17-year-old Trayvon Martin, who had the audacity to stroll through a gated community in Florida in a hoodie, carrying a bag of candy and a can of soda.

He was shot dead by George Zimmerman, a neighbourhood vigilante who has since proven to be something of a habitual criminal himself.

Zimmerman, who cited Florida's pro-gun "stand your ground" defence, was acquitted, and three angry young black activists founded Black Lives Matter, and began making some noise.

Black Lives Matter

Since then, chapters of Black Lives Matter have opened across America.

They are politically unaffiliated, but so vocal and so effective that police unions and conservative groups, among others, have come to despise them.

Are they mouthy and offensive? Absolutely. Conservative activists have taken to filming them as they march into shopping centres, disrupting Christmas tree lightings and "Black Friday" shopping frenzies.

A different kind of BLM protest, this one with many white faces, marched through downtown Seattle and two of its malls on Friday to bring attention to police brutality, civil rights issues and consumerism. (Genna Martin/seattlepi.com/Associated Press)

It's the "all lives matter" retort, though, that is arguably the most pernicious counterattack by the political right.

Its potency is the inherent suggestion that the Black Lives Matter protesters are elevating the value of African-American life over everyone else's.

In fact, they are fighting against the clear fact that black lives matter less — that racism exists in many of America's institutions. The U.S. president, no less, has said as much.

As one protester put it, if all lives really did matter, there would be no need for Black Lives Matter.

At the forefront of the counterattack: Donald Trump and his simplistic band of admirers.

Some of them actually chanted "all lives matter" at a Trump rally late last month, as other staunch Republicans in the crowd kicked and punched a Black Lives Matter activist who had the nerve to show up and heckle a politician known for racist statements.

Later, Trump said the guy probably deserved what he got.

Just a few days after that, on television, Trump was clear: to him, "all lives matter."

A postscript: There is one Black Lives Matter chapter outside the U.S., in Toronto, where racially tinged police shootings have occurred.

But, says spokeswoman Sandy Hudson, the Canadian chapter is hobbled.

Data, she says, is compiled differently in Canada. Race isn't considered in statistics the way it is in the U.S.

"The black community knows these things are going on, because we are affected," she says. But "when people ask us to prove it, it's difficult."

Difficult, but impossible to dismiss. Is Canada better? Ask the indigenous leaders who have been seeking an inquiry into their nearly 1,200 missing and murdered aboriginal women over the past 30 years.

All lives may indeed matter, just some a lot more than others.