But the second important lesson is that, perhaps surprisingly, confronting the links between ethnicity or culture and crime doesn’t necessarily change the response all that much.
The New Year’s Eve attacks are shocking at least partly because they’re confusing. If they were primarily sexually motivated, done for kicks or fuelled by assumptions about western women’s sexual availability, then surely there would be no reason to steal the victims’ valuables. Rapists seek power, not money.
But if these were primarily robberies, and the groping just a novel way of disorientating victims long enough to pick their pockets, it’s odd that some of the assaults were reportedly so serious and that not all victims lost valuables. Perhaps different crimes are simply being lumped under one umbrella, but as with the mob assaults on women, including journalists covering protests in Tahrir Square, where sexual opportunism was hard to distinguish from political intimidation, this feels like a new phenomenon.
Liberals shouldn’t be afraid to ask hard questions. Young German women thankfully enjoy historically unprecedented economic and sexual freedom, with their expensive smartphones and their right to celebrate New Year’s Eve however they want. The same isn’t always true of young male migrants exchanging life under repressive regimes, where they may at least have enjoyed superiority over women, for scraping by at the bottom of Europe’s social and economic food chain. It is not madness to ask if this has anything to do with attacks that render confident, seemingly lucky young women humiliated and powerless. But even if it does, the answer wouldn’t be to halt immigration – even if that were possible, which it isn’t regardless of whether Britain leaves the EU – just in case a few immigrants are sexually aggressive, any more than the answer to Savile is to keep all men away from children.
 
Too often anti-immigrant feeling stems from what’s really a long-running failure of the state – to protect children at risk, to provide enough social housing or school places, to police what has reportedly been a rough area of Cologne for years – which becomes more visible as the population grows. And since that growth can’t be turned on and off like a tap, whatever some politicians say, the answer is for governments to do what we elect them to do: rise to the challenge, calm the fear that breeds extremism by demonstrating they can cope.
Which in this case means treating this crime wave exactly as they would any other: policing more effectively, with extra manpower if necessary, and being upfront at all times about doing so. Bluster and blame fools nobody. But neither, it turns out, does queasy silence.