Violent Islamist attacks on Jews in mainland Europe are causing acute concern. But fanatical religious belief which creates the impulse to murder Jews in the service of God, however appalling and terrifying, is not hard to grasp.
What is even more unsettling is that people from the European mainstream, who have gone to great lengths to show they have learned the lessons of the Holocaust, or who display affection for the State of Israel, or who are obsessed with anti-racism and human rights – that such people are now coming out with unhinged Jew-hatred.
Two countries in particular are repeating this dismal European history: Britain and Poland.
In Britain, the Labour party is in the grip of an existential crisis over the revelation that it is riddled with antisemitism. In extraordinary scenes in Parliament this week, Labour MPs rounded on their leadership for continuing to deny the appalling prejudice on display in the party and revealed the threats and intimidation against those MPs who have taken a stand against it.