It’s NOT just a state of mind, Flyer. There are very serious economic and social consequences that can (and often do) arise from “forced” multiculturalism without integration…or fairly strict segregation into these ethnic/cultural communities, but that’s not legal.
Some multiculturalism is good, but as mentioned above, not all immigration is the same, and not all immigration is beneficial. Also, you don’t necessarily need to move massive numbers of people around in order to encourage global trade (beyond those directly associated with trade).
Those in Europe who are opposing the massive immigration that is harming their own culture and way of life might manage to either reverse the immigration trends or find a way to make it less harmful to them and their social/economic systems. I like they way Australia’s immigration laws work.