I shall begin by defining the immigration type in question, namely *mass* immigration. This form of immigration is random; no immigrant is accounted for, neither by skill or education. There is absolutely *no* European country that has had a net benefit from this sort of immigration. Rise in crime, polarization of cultural groups, etc., have all been observed in *all* countries experiencing mass immigration.
Europe should only take in people temporarily, and those who are highly skilled (with a deportation clause). End.
In England, in the 1960s, there was a really smart and prescient politician named Enoch Powell. He generated some notoriety by basically saying, "You are letting all these people in, and you're going to pay for it, later." He was right.
If one wants to emigrate, and one is schooled, highly motivated, is willing to assimilate into the new country, etc., that is one thing. But to simply let in "so many of these," and "so many of those," or to have no restrictions at all, is just foolish.
The rise in crime and the polarization of cultural groups is a good observation. On balance, the average person within the mass immigration becomes a net negative to society, rather than a net positive. Far too many of them want to take what they can, from the new country, while ignoring the duties and responsibilities that are asked of them. They don't want to really become part of the new country, rather - they want to maintain their old culture, even set up zones within the new country where their differing laws would hold sway.
The EU and Democrats of the American political system seem to have this incessant idea that everyone is equal, evil is curable with a prescription of 2 apologies a day, and Hitler wasn't really bad he just needed a hug. Dear Politicians; we all understand that you live in high-end gated communities with armed security on site plus your Secret Service detail guarding you, but we don't. Chapo Guzman -- research him then explain why it is you think open boarders are a good thing. What if he comes over the boarder in a group?