Where exactly does the boundary lie between tolerance and heedlessness? If you were sticking a pin on a map, you'd want to aim for De Wallen - otherwise known as Amsterdam's red-light district. This is where tourists go to gawp at the most famous and visible manifestation of Dutch tolerance: the prostitutes who pose half-naked in crimson windows, hoping to lure in the punters.
Foreigners are fascinated by the Netherlands' permissive attitude to sex and drugs. Around 18 million tourists visit Amsterdam every year, smoking legal weed in its coffee shops and ogling (or more) its legal prostitutes. The Dutch put up with this - the selfie-snappers and the stag parties retching into the gutters - not just because it is profitable, but because enlightened libertarianism is a kind of national religion.
"Amsterdam prides itself, and rightly so, on its wholly liberal and tolerant attitudes," reads one Dutch tourism website, "embracing the fact that people may be into prostitution, soft drugs and pornography. And that it is only human."
But is "only human" the best that can be hoped for? The one time I walked through Amsterdam's red light district, I found it unutterably depressing. Many of the windows contained nothing but an empty chair drenched in neon blood, like a reproachful art installation. Of the few working girls I saw, not one was smiling. Most looked bored. Just by being there, trying not to stare, I felt myself to be participating in something both human and ugly.
I'm glad it's not just me. Femke Halsema, the first female mayor of Amsterdam, has caused a very Dutch kind of scandal by suggesting that tolerance alone isn't enough. She points out that around 80 per cent of the women in Amsterdam's windows are migrants, mostly from poorer countries.
Sex trafficking to the Netherlands has more than doubled since brothels were made legal in 2000; and even when prostitutes haven't been trafficked, "you can question their free will, because there is a huge need for them to feed families elsewhere".
The fact that these vulnerable women have become a tourist attraction is the last straw. "I cannot accept this kind of humiliation of women," says Halsema. "I cannot stand it."
These sentiments - and especially her suggestion that the red-light district should be moved outside the city, to a specialist complex that could be better regulated - have caused alarm. Sex worker unions protest, truthfully, that Amsterdam is one of the safest places in the world in which to sell your body.
But what makes Halsema's agenda truly subversive is nuance: the least fashionable of political virtues. She is a liberal politician who herself voted for the legalisation of brothels. She has no desire to change the law back. She is merely insisting that its effects should be examined honestly. In the same way, she says, middle-class drug users need to realise that their private hedonism has wider consequences.
"They should know that the young boy who comes and brings their pizza and cocaine is in danger of getting into a drug environment that is very dangerous to him, that could get him killed."
Even liberalism can sometimes be a trap - especially for those with the fewest options. Halsema sums up her philosophy with a quote from Janis Joplin: "Freedom is just another word for nothing left to lose."
The Telegraph, London