If you recall, Angela Merkel encouraged the acceptance of a million illegal immigrants into the EU during the Syrian war. The vast preponderance of them were young males, and by no means all of them were from Syria. Many were culturally very different from most Europeans. A substantial number have not integrated.
This has ongoing reverberations, not least that Sweden has moved to the right. Apparently, even liberal Sweden found that its generous welfare system couldn't absorb a huge wave of people many of whom were not there to work or to enjoy Swedish culture. Some brought violence with them. And now Sweden has a far right government.
Personally, I am keen on benign, legal immigration, but it's all about the rate at which it is done and the attitude of the immigrants. But if folks on the left don't listen and respond to people's concerns over immigration issues, you empower people you may not wish to.
Immigration isn't only about immigrants. It's about the people in the place they are coming to and their interests.
http://www.dailymail.co.uk/news/article-11221319/A-shootout-playground-migrant-gangs-reveals-Sweden-turning-liberalism.html