Parallels have been drawn this week between the massacre in Paris, and the siege in Sydney last month.
Both were brutal, appalling attacks on innocent people.
But there's another connection which puts the perpetrators on different sides of a crucial debate.
A few cartoons in response to this week's attacks have played with the idea of the pen versus the sword: that freedom of speech is vital in a free, democratic society. Offence is, often, an inevitable, necessary by-product.
'"I am Charlie" might be a modern-day paraphrase of Voltaire's famous line: "I disapprove of what you say, but I will defend to the death your right to say it."
I was reminded of someone else who used a version of the pen/sword analogy. Before he became gruesomely infamous for his bloody siege in Sydney, Man Haron Monis' most famous TV appearance was a rant outside a Sydney court where he invoked his own version of the phrase.
"This pen is my gun and these words are my bullets," he said, waving a pen in the air.
Monis had written deeply offensive letters to families of soldiers killed in Afghanistan letters that, in the words of the court, referred to husbands and sons in a "denigrating and derogatory fashion". He called the dead soldiers "pigs" and "murderers". He'd urged their families to petition the Australian government to remove its troops from Afghanistan.
Nasty stuff. But illegal?
Well, in Austraila, yes. Although only just.
Monis was convicted under an Australian law that prohibits using the postal service in a way that "reasonable persons would regard as being, in all the circumstances, menacing, harassing or offensive".
Monis appealed. He claimed the law violated his right to freedom of speech.
New South Wales' Supreme Court found against Monis, twice. So he appealed to Australia's Federal High Court.
It split: three of six appeal court judges said Monis' offence was constitutional: that the conviction should stand. But three judges did not – agreeing, essentially, with Monis that his conviction violated his freedom of speech.
Needing a majority of judges to overturn the lower court's decision, though, Monis' conviction stood.
And, later, Monis - sickeningly - expressed himself not with pen – but with real bullets and a real gun.
Monis was a deranged man with a criminal history. He was facing charges in connection with the murder of his ex-wife, and a number of other charges of sexual assault.
But on the narrow issue of freedom of speech, he was – on paper – on the same side as those supporting the right of Charlie Hebdo to print what it wanted the right to free speech – the right to offend.
For sure, Monis' letters were particularly appalling because they were sent directly to grieving families. They were deeply offensive. But some found Charlie Hebdo's cartoons just as offensive yet no-one successfully prosecuted the cartoonists for those.
Support for free speech - support for the right to offend - can't just be invoked when it's not you being offended. Nor, for that matter, when it's not the majority taking offence, or even "reasonable person".
Australia's High Court split evenly. Three judges decided that, however offensive, Monis did have the right to write foul letters. Those three judges, one assumes, would have fully backed the Charlie Hebdo cartoonists had they published in Australia.
But the other three judges? The ones who decided Monis' did break a constitutionally-valid law? Where would they sit? And, given that it was their judgement that prevailed in the Monis case, what does that say about freedom of speech in Australia?
Can Australians really say their constitution – or their judges - let them '"be Charlie'"too?
UPDATE: People in Comments have pointed out – rightly – that there is a difference between publishing a magazine with offensive material, and using the postal service to target – and offend – a specific person. The Australian law I refer to my blog is relevant for the latter but not for the former. My point was as millions join forces around the world to claim "Je Suis Charlie", different laws in different places would make putting that sentiment into practice difficult. As Human Rights’ Commissioner Tim Wilson has said today, Australia also has laws - specifically the so-called 18C clause of Australia’s Racial Discrimination Act– that would probably make it illegal to publish an offensive magazine like Charlie Hebdo here. For good or ill, actually "Being Charlie" – as anything more than a slogan - could be hard in Australia.