It's not the word Jeremy Corbyn used to describe the death of one of history's worst mass murderers - a "tragedy" was his analysis of the killing of Osama Bin Laden - but the moral equivalence. What he actually said was "This was an assassination attempt, and is yet another tragedy, upon a tragedy, upon a tragedy. The World Trade Center was a tragedy, the attack on Afghanistan was a tragedy, the war in Iraq was a tragedy".
The death of those people who hurled themselves from their windows rather than burn alive. The killing of the man who praised his God when he saw the footage of their final moments. Both events "a tragedy" in the eyes of Labour's next leader.
But it won't make any difference. It will just be shrugged off again. Words taken out of context. Another Tory media smear.
One of the paradoxes of the last few weeks is how, to Corbyn's supporters, the worse things have got, the better they have become. The association with Holocaust deniers, the speaking engagements alongside those cheering the death of British soldiers. They have strengthened, not weakened, the resolve of the faithful. "Look at everything they're throwing at him, and still he's standing tall!"
Actually, it's not just Corbyn's devotees who are saying that. Many neutral observers are in awe of his ability to cheat political gravity. The daily revelations emerging from the archives of Russia Today and Press TV would derail any other politician's bid for the leadership of their party. The fact they haven't is proof that Jeremy Corbyn isn't a mere politician, but a political phenomenon.
No. He isn't. He really isn't.
At the end of next week, Corbyn will win the Labour leadership election. And when that happens people will need to grasp what his victory means. More importantly, they're going to need to grasp what it doesn't mean.
One of the first things people will have to understand is that though he will have won, Corbyn will not have been elected Labour leader. Labour will not have a leader. Corbyn will not command the support of his shadow cabinet, or his MPs. Nor does he want it. His appeal - and he's been entirely open about this - will be to the activists and members who have elected him. They will decide policy - not him. They will dictate his political direction - not him. A small hard-left clique will establish an iron circle around him to "interpret" the activists' will. But Labour will not have a leader. It will have a cipher.
The other thing it will be necessary to recognize is that despite the bombastic claims of his acolytes, his election will not represent a redrawing of the political rules. The rules remain in place. Corbyn and his supporters have simply chosen to ignore them.
The British people have registered his comments on Bin Laden. His links with those who welcomed the killing of men and women who laid down their lives serving their country. His statement that "paying tax is not a burden". Or if they haven't, they will when the Conservative campaign machine cranks into gear.
Corbyn's tribunes know all this. But they don't care. They're aware his statements and stances make him unelectable. They couldn't give a monkey's.
Corbyn hasn't miraculously cleared a hurdle other mere politicians would find insurmountable. He's run round it. He'll be disqualified as a result, and his supporters know he'll be disqualified. But they just want to see him run.
Which is why we have to understand something else about Corbyn's impending election as leader of the Labour Party. We've now reached the point where it isn't really possible to call Labour a political party at all.
Political parties exist to win elections, form governments and then implement policies. It's what defines them as political parties, as distinct from protest groups or debating societies. But election victories and government are no longer relevant to Labour. Policies are now just a stakeholder engagement tool - a means of establishing a connection with the only section of the electorate that matters, the newly registered base of activists.
Even sensible Labour MPs and supporters now chastise themselves for arguing power should be a priority. "Saying 'we have to win' isn't enough", one centrist shadow cabinet member told me last week.
Maybe it isn't. But for a serious professional political party that aspires to the governance of its nation, it should be.
Jeremy Corbyn is not a political phenomenon. He is not actually a politician at all. He's an ideal. A dream. The political equivalent of a child's invisible friend.
And as such he is indeed invincible. As his supporters are fond of pointing out, you can't kill an idea. Until you get to polling day.
People who describe Osama Bin Laden's death as "a tragedy", or speak alongside those who welcome the death of British soldiers don't get to lead serious mainstream British political parties. And Jeremy Corbyn's election next week will prove it.