At a restaurant in Knightsbridge last week, I saw more Arabs on the streets than I do when I am in Dubai Mall in the Emirates. I am proud that London is the top holiday destination of choice for our Arab friends. On holiday, most of the young Arab women discard their face veils (niqab), black cloaks (abaya), and men do away with white robes to enjoy the freedoms offered by our city. Muslims from around the world hold London in high esteem and wish to send their children to our universities.

I have just returned home to London after three years of living in New York. There, I met American Muslim leaders fully at home in the US and among the most patriotic Americans I know. They support their soldiers at home and abroad. Jews and Muslims dine together in kosher restaurants and major mosques are twinned with synagogues to display mutual respect.

But what I see and hear among activist Muslims in London worries me. At mass demonstrations for “Free Palestine” at the weekend, some chanted, “Obama, what do you have to say? How many kids have you killed today?” on a day when the US government was trying to rescue Yazidis in Iraq. If Palestine is to be freed, it should be freed from Hamas.

Socially, there is the rise of children at primary schools across the capital wearing hijab, or headscarves. This is a sign of separatism, a desire to assert difference from other children decided by parents. I see niqabs or face-covers for women, and British Asian Muslim men wearing Arab clothes that our visitors from the Gulf readily discard. How did we become silent at this physical changing of our city’s face?

Politically, being visibly Muslim is fast becoming a statement of rebellion. America led the wars in Iraq and Afghanistan, and yet American Muslims did not ally with the far Left to protest against imperialism. In the US there is no far-Left movement of significance. Here, in London, the despicable Socialist Workers Party, in bed with George Galloway’s Respect party, has led a generation of young Muslims into the politics of opposing British foreign policy, rejecting Israel’s legitimacy, to the extent that UK Muslim leaders refused to attend Holocaust Memorial Day for years.

A widespread anti-Americanism, a deep anger, has been seeded amid many Muslims. Israel’s actions have made matters worse.

Baroness Warsi’s resignation last week, while a matter of conscience, is a nod to this collective rage. Galloway’s comment that Bradford must be an “Israel-free zone” reflects the worst elements of this new politics. Liberal Democrat MP David Ward, seeking Muslim votes in Bradford, had to outdo Galloway by wishing all of the UK become “Israel-free”.

This ugly politics is not only about Israel but helps create an atmosphere which threatens our Jewish citizens, who have already reported an increase in anti-Semitic activities.

Londoners and London’s Muslims must change course, and soon. Where we lead, the country will follow. London is home to nearly a million Muslims. Together, we can stop tolerating this new extremism in our midst and learn from the openness of London’s Muslim tourists and our American cousins. This new Marxist-Islamist axis must be broken.

Ed Husain is an adjunct senior fellow at the Council on Foreign Relations (New York) and a senior adviser to the Tony Blair Faith Foundation. Twitter: @ed_husain