Immigrants or Muslims?

When exactly did Europeans cease to refer to immigrants from the
Mediterranean as 'Morroccans', 'Arabs' or other national designations
and adopted the general term 'muslim'?

More to the point: why? After all, these 'muslims' have been among us since the 70s. Are we only discovering now that theirs is not a Christian religion? And why do we only do that to them?

One explanation, often heard, has to do with the salience of nuisance. The neighbors at the place I used to live were Jehova's Witnesses (yes, very anoying), but we would not refer to them as Jehovas except when we were discussing their slightly excentric habits in proselytizing. So only when they were a nuisance did we refer to their religious commitments. Similarly, the argument goes, since a lot of the problems Europeans face with their migrants are due to their religion, we refer to them as muslims. Ayaan Hirsi Ali would be someone arguing this.

However, this argument clearly is incorrect. Many of these migrants are muslim in the same way that I am Catholic: only at Christmas (or Id al-Fitr -- the end of Ramadan) and perhaps when there is a baptism or burial. So it is unlikely that the problems that spurred the riots in France for example are religion based. Furthermore, this would in fact be a reason to insist on the label 'Moroccan', 'Arab', etc.

Of course, many of the migrants have had children and are truly settled and have taken on the nationality of their new country (if possible; not all countries are very welcoming in this regard.) So, really, they now are Dutch, German, Belgian, French, or what have you.

In short, I am puzzled. I know that the shift occurred sometime after 9/11, under the influence of fear for fundamentalists, but, really, why? Why are the Europeans so afraid that they change the nomenclature for a good 10% of their population in ways that would be considered deeply insulting, stigmatizing and, in general, unhelpful when applied to Catholics.

And lets face it: Catholics are the real pests.