Naila Keleta-Mae is a professor at the University of Waterloo where she researches race, gender and performance.

Tonight, the group The Tenors altered the wording of the Canadian National Anthem when they sang it at the 87th Major League Baseball all-star game. "We're all brothers and sisters. All lives matter to the great," they sang as one of them held up a sign that read "All Lives Matter."

Two days ago, Rudy Giuliani, a former mayor of New York City, said that the sentiment of black lives matter is inherently racist, and that people should instead say "all lives matter."

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Let's be clear, "all lives matter" is a false claim that can only be made if you actively choose to ignore that anti-black racism has and continues to exist in the United States of America.

The hashtag #BlackLivesMatter was created on Twitter in July 2013 by black queer women Patrisse Cullors, Alicia Garza and Opal Tometti in the wake of George Zimmerman's killing of 17-year-old Trayvon Martin.

A recent study of the hashtag's use on Twitter, done by scholars Charlton McIlwain, Deen Freelon and Meredith Clark, reveals that for more than a year it was essentially dormant and only rarely used. But, on November 24th, 2014 something changed. That night, a grand jury decided not to indict Darren Wilson, the white police officer that shot and killed Michael Brown, a black, unarmed 18-year-old in Ferguson, Missouri. Within 24 hours, the hashtag #BlackLivesMatter was tweeted more than 100,000 times and it and its derivatives have since been tweeted more than 40 million times.

So, what changed? Why did the simple, common sense statement that black lives matter go from barely used to defining an era's fight against institutionalized anti-black racism in the United States and beyond?

Because the grand jury's decision that night was widely understood to reflect what has been true for centuries in the United States: that state-sanctioned violence against black people is acceptable and that those who perpetuate it will be protected. The words - and then the organized activist group Black Lives Matter - stood as a reaffirmation of what is obvious in theory and yet continuously contentious in practice.

And it's not new for black people to craft a clear and catchy slogan to bridge the gap between theories of equality and practices of systemic injustice. In the mid to late 1900s it was "Black is beautiful," "Black power," and "Say it loud, I'm black and I'm proud." Certainly, all people are beautiful, all people should have access to power and all people should feel proud. But, that's not how whiteness and blackness are lived in the United States.

There's a long list of the recent killings of black people by police officers in the United States: Sean Bell (23-years-old), Rekia Boyd (22-years-old), Philando Castile (32-year-old), John Crawford (22-years-old), Malcolm Ferguson (23-years-old), Jonathon Ferrell (24-years-old), Ezell Ford (25-years-old), Eric Garner (43-years-old), Oscar Grant III (22-years-old), Aiyana Jones (7-years-old), Kathyrn Johnston (92-years-old), Tamir Rice (12-years-old), Delrawn Small (37-years-old), Yvette Smith (45-years-old), Timothy Stansbury (23-years-old) and Alton Sterling (37-years-old).

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Some of the interactions with police officers that led to the killings included: talking loudly, opening the front door, and playing in a park. To state the obvious: interactions with the police on matters such as these should never result in death because in theory black lives matter, in theory the state recognizes this and in theory the state protects everyone equally. But in practice, as countless studies have concluded, anti-black racism persists in policing.

When faced in 2014 with what was widely understood as yet another iteration of the same violent dynamic that has long persisted between the state and black people – #BlackLivesMatter did what black slogans that address anti-black racism in political, economic, and social spheres have long done. It spoke back to the state, it referenced history and it aspired to the future.

So no, stating "all lives matter" is never an appropriate response to the assertion that "black lives matter" for those with even an inkling of understanding of how anti-black racism has and continues to impact the United States.

And no, inserting "all lives matter" in the Canadian National Anthem is never an acceptable act for anyone with even a modicum of understanding of how discussions about anti-black racism in the United States inform discussions about anti-black racism in Canada.

What is a thoughtful response to black lives matter, especially from non-black people? Affirmation and action – say "Yes, black lives do matter" and then challenge instances of anti-black racism in private and public every day life.

Editor's Note: The original version of this column incorrectly identified Renisha McBride in the list of black Americans killed by police. In fact, she was killed by a civilian. This version has been corrected.