The problem with statements like "Europeans are concerned about Muslim immigration" is, there's no such thing as "Muslim immigration", nor do any but a minority of conspiracy theorists really think about immigration in those terms on a day-to-day level. Immigrants do not come from Muslimland, bearing Muslamic mores and culture, they come from Algeria or Pakistan or Turkey or Syria, and the tensions originating which emerge are not between "Europeans and Muslims", as if these were terms that in any meaningful way describe how people live their lives, but between Frenchmen and Algerians, English and Pakistanis. (Which, I'll grant, are only marginally less ridiculous descriptions.) And, on an immediate level, people kinda-sorta know this, insofar as what they take offence to is not an abstract category of "Muslim", but whatever particular points of difference they encounter.
"Muslim" is an after-the-fact categorisation, a way of stringing local tensions into a grand (and grandiose) narrative of civilisational struggle, rather than a series of comparable but basically independent failures of public policy. So people take the Muslims they are familiar with, and whatever basket of stereotypes and prejudices they carry regarding these local Muslims, arbitrarily generalise these preconceptions from Timbuktu to Jakarta, and imagine that this invented fiction of homogeneity is proof of a monolithic Islamic civilisation, because that's just about good enough for them to convince themselves that the story holds. They're not getting all hot and bothered about immigrants because they're concerned about Islam, rather, they affect concern about Islam because they don't like immigrants.
Hannah Arendt observed the mistake of Weimar liberals in trying to engage with the claims of anti-Semites as if they were attempts to state an actually-existing truth, where in fact they were statements of what the anti-Semites needed to be true for them to get away with what they intended to do to the Jews. Though I walk in the valley of the shadow of boring white dudes yelling "oh, so everyone you don't like is a Nazi", I will fear no evil, because I think it's worth thinking about the narrative of "Europe vs Islam" in those terms.
revised about four hundred times within 20 minutes of posting, in case anyone happened to quote an earlier version.