The words Black Lives Matter have featured prominently in the news over the last fortnight since the tragic death of George Floyd in Minneapolis. It was a terrible way to die and three police officers have appeared in court.
That slogan 'Black Lives Matter' first appeared as a hashtag on social media in 2013 after George Zimmerman, a neighbourhood watch coordinator, was acquitted of the murder of black teenager Trayvon Martin in Florida.
Black Lives Matter then became a movement and it gained fresh impetus the following year after the deaths of two young men in police custody, one in St Louis and one in New York City.
Since then it has appeared in the news sporadically, including an intervention in the last US presidential election.
The man who shot Trayvon Martin in 2013 was not a police officer, but since the two deaths in 2014 Black Lives Matter has had a particular focus on the deaths of black Americans while in police custody or as a result of police actions.
According to the Black Lives Matter website: "People were hungry to galvanise their communities to end state-sanctioned violence against black people."
The focus of Black Lives Matter is on "state-sanctioned violence against black people", and that raises some important issues and questions.
The US police are more likely to use lethal force and people are more likely to die in police custody than in most other developed countries.
For example, the rate of in-custody deaths in the USA is six times that in the UK.
International comparisons are difficult because of the different ways the figures are collected and presented, but the overall picture is clear.
It is also clear that a disproportionate number of black Americans are killed in police custody.
According to a 2016 study, black men are nearly three times more likely than white men to be killed by police intervention.
But what about violence against black people that is not "state-sanctioned"?
As a starting-point we have to acknowledge that the USA is a more violent society than the UK.
There are cities in the USA where the murder rate per capita is 20 or 30 times that of the murder rate per capita in London.
However, the homocide rate for black men in America is 3.9 times the national average, and around half of all known murder victims are black.
That is a shocking figure, but it is only part of the picture because the perpetrators of those crimes were overwhelmingly black Americans.
In 2018, where the victim was black, the suspected perpetrator was also black in almost 90% of the cases and that has been the pattern year after year for decades.
Most of the black people who are killed in America are killed by other black people, just as most of the white people who are killed in America are killed by other white people.
Murder is much more likely to be intra-racial than inter-racial, and far more black Americans are killed by other black Americans than are killed by the police.
The focus of Black Lives Matter on "state-sanctioned violence", whether intentionally or unintentionally, takes the focus off the overall issue of crime in black communities and so perhaps a better message might be All Black Lives Matter, whoever the killer, whoever the perpetrator. The tears of a mother whose son has been killed in gang warfare or a drive-by shooting are just as important as the tears of a mother whose son has been killed by a policeman.
All Black Lives Matter. There should be no hierarchy of victims and no hierarchy of concern.
There are issues that need to be analysed and addressed, but when Black Lives Matter puts it all down to "white supremacy" their analysis is wrong.
Moreover, the situation is not helped by some of the things we have seen on this side of the Atlantic, where a genuine case has been hijacked by fringe radicals - and not just the tooled-up anarchists in Bristol.
People Before Profit councillors in Galway have actually demanded the removal of a memorial to Christopher Columbus because he was "genocidal" and the statue "glorifies slavery".
Unfortunately, in this - as in many other issues today - it is difficult to have the thoughtful conversation that it deserves.
And that is to the detriment of us all.