In 1994, I was robbed and beaten at knife point in Moscow. Russian friends were horrified -- and angry, because the assailants were migrant Chechens from the North Caucasus.

Over the weekend, that latent anger and resentment among native Muscovites boiled over. A protest at the stabbing of a young Russian taxi driver degenerated into an attack on a vegetable warehouse staffed by migrants from the Caucasus and Central Asia. Police quickly released the rioters they had detained and arrested more than 1,600 migrant vegetable market workers -- the victims.

The most common explanation for this backward police response is that the government wants to calm the nationalist right and xenophobia more generally, by demonstrating it is alive to the threat from the country's 11 million immigrants (second only to the U.S.). It is a doomed policy, immoral, unjust and in no way peculiar to Russia.

Across Europe, anti-immigrant and far right political parties have been gaining support during the economic downturn. In France, Marine Le Pen's National Front party won a local by-election in Provence on Oct. 13, stunning the mainstream parties of the left and right. In Austria, the anti-Muslim Freedom Party boosted its share of the vote to 21 percent in national elections last month. In the Netherlands, Gert Wilders's far right Party for Freedom is making a comeback in opinion polls.

So worried has U.K. Prime Minister David Cameron become by the threat from the anti-immigrant and anti-European Union United Kingdom Independence Party that he has cracked down on visas for foreign students (source of a great business for U.K. universities), pledged to end so-called benefit tourism (the alleged practice of immigrants traveling to the U.K. to take advantage of more generous state handouts) and dispatched vans to cruise parts of London displaying large advertisements that tell illegal immigrants to "Go home or face arrest."

The biggest surge of support for the most extreme party has come in Greece, where the neo-fascist Golden Dawn was until recently scoring upward of 14 percent in opinion polls. Greece's weak and unpopular government sought to draw voters away from Golden Dawn by adopting some of its anti-immigrant rhetoric, rounding up paperless immigrants and throwing them into hastily organized internment camps. Police allowed Golden Dawn thugs to roam free and attack immigrants with impunity.

These policies of co-option don't work. They legitimize xenophobia rather than sucking out the poison. Over the past year, during which Cameron took all those steps aimed at eliminating the threat from UKIP, support for the party rose from 7 percent to 11 percent, according to a Yougov/Sunday Times tracking poll.

In Greece, Golden Dawn's support doubled after last year's parliamentary election, when it won 7 percent of the vote (up from 0.29 percent in 2009). It took the fatal stabbing of an ethnically Greek, anti-fascist rapper by a Golden Dawn member last month to force the government to change course and arrest the party's leaders. Golden Dawn's support fell back to 7 percent after the stabbing.

Most anti-immigrant arguments are myths. A fact-finding report commissioned by the EU this week found that migrants within the EU suck up only 1 percent of benefits in the host countries and 0.2 percent of total health-care spending, less by proportion than the native population. Other studies have found migrants to be solid net tax contributors -- naturally, because they come to work.

Governments need to tell the truth about migration and deal with its ill effects. There are criminals among migrants, as in all populations, and it makes people angry when the police appear powerless, incompetent or unwilling to address that problem. The two Chechens who followed me into the stairwell of my apartment block in Moscow took my clunky laptop and wallet. We got to talking about their president of the time, Dzhokhar Dudayev, whom I'd recently met. (I wanted to distract them, because they wanted the keys to my apartment, where my girlfriend, and now wife, was waiting.)

A third mugger, the lookout, inflicted the damage, coming into the stairwell high on drugs to see what was taking so long. He asked the other two for their knives, repeatedly. They refused and dragged him away. I have mixed feelings about these particular migrants, still.

(Marc Champion is a Bloomberg View editorial board member. Follow him on Twitter.)