Probably the wrong word. Deep fears? I think as long as there is prosperity and some sane media and education you can have immigrants / refugees. But we've seen a big rise in numbers over the last two decades and face economic doom. Some European countries are now 5-8% Muslim (even though only like a quarter are actually practicing). I don't think it's so much that they are different, it's that people fear there won't be enough for everyone. And neoliberal policies do love immigrants to depress wages. And imperialist conflicts in the last decades have produced refugees en masse. Plus a gigantic wave due to climate change.

Ideally Europe would massively invest into technology to produce more food / calories on minimal land, clean water and how to build massive green metropolis's with very low energy footprint and circular economies that can sustain themselves mostly. So we can harbor refugees in Europe or build these cities in their home countries. The alternative is genocide.