On a wall in the heart of the Cathedral Quarter (leading showcase of our new, tourist-friendly Belfast) someone has daubed a Star of David. '9/11' it reads. 'Jew job'.
A blunt summing up there of the perverted argument, routinely sucked up by internet idiots, that Jews (Israel, of course, specifically) were behind the Twin Towers massacre.
The graffiti may not be as in your face as those TV documentary scenes of Ukrainian football fans (joint hosts of the Euros) chanting Sieg Heil. Or as wordy as much of the anti-Jewish commentary that currently gushes forth from both right and left across Europe.
But like a gross little boil oozing bile it is a reminder that, here too, anti-Semitism in all its many forms, spreads like an infection.
Even the expression anti-Semitism is routinely challenged today, as if calling it something else might make it seem less.
So maybe we should just call it for what it is. Jew-hating.
And right now, right across Europe, hatred of the Jews is the big crowd-puller.
Like football it's a game of two parts. The far right hate the Jews. Many on the left hate the Jews too. The Jews just can't win.
And the starkest reminder of the enormity of what they have already lost and where such hatred can lead is in one of the countries where the Euro finals are being played.
Wayne Rooney was among a group of England players who in recent days visited Auschwitz. the notorious Nazi death camp just outside Krakow.
Because the footballers were photographed by invited media during their visit, this has led to accusations that the trip was more a PR stunt aimed at sanitising the often tawdry image of football than a genuine desire to remember and pay tribute to the hundreds of thousands of men, women and children herded to their murders in the gas chambers.
A PR aspect may well have been part of the motive - who knows what goes through the mind of football officialdom? - but as 'stunts' go this one at least highlights something much bigger than the game.
Rooney was photographed leaving the museum looking thoughtful and solemn. He did not look totally traumatised.
The Auschwitz Museum does not set out to totally traumatise. (Although, God knows, it would be easy to do so). It is a place which everyone should try to visit at some point in their lives because it aims to educate and inform, to show something of the scale and horror of what happened in 20th century Europe and to warn against the mindset and the hatred that led to it in the first place. Never again.
And yet once again, the same vile racism that led to the Holocaust burbles and blazes right across Europe. Once again Jews (and in an updated twist, the Jewish state) are blamed for just about every evil of the age from the world's economic woes to an al-Qaeda atrocity.
The neo-Nazi football fans of the Ukraine taunt each other with cries of 'Jews!' not because members of the other team are actually Jewish, but because that's about the worst insult they can think to hurl.
The leftie Jew-haters who believe themselves more sophisticated in their sneaking anti-Semitism single out Israel, the Jewish state, as the world's Great Satan. On the right, Jew-hating is fanatical; on the left, it's fashionable.
But right across this spectrum of venom and prejudice runs the old libel - it's all a 'Jew job'.
If you were Jewish in Europe today, knowing all that's gone before and knowing what is always possible again, wouldn't you too be fearful of the writing on the wall?