Bret Stephens writes:

For Muslim voters in Europe, the attractions of the Socialists are several. Socialists have traditionally taken a more accommodating approach to immigrants and asylum-seekers than their conservative rivals. They have championed the welfare state and the benefits it offers poor newcomers. They have promoted a multiculturalist ethos, which in practice has meant respecting Muslim traditions even when they conflict with Western values. In foreign policy, Socialists have often been anti-American and, by extension, hostile to Israel. That hostility has only increased as Muslim candidates have joined the Socialists’ electoral slates and as the Muslim vote has become ever more crucial to the Socialists’ electoral margin.
More mysterious, however, at least as a matter of ideology, has been the dalliance of the progressive left with the (Islamic) political right. Self-styled progressives, after all, have spent the past four decades championing the very freedoms that Islam most opposes: sexual and reproductive freedoms, gay rights, freedom from religion, pornography and various forms of artistic transgression, pacifism and so on. For those who hold this form of politics dear, any long-term alliance with Islamic politics ultimately becomes an ideological, if not a political, suicide pact. One cannot, after all, champion the cause of universal liberation in alliance with a movement that at its core stands for submission.

More here.