The problem is that the politicians have made a lot of promises over the years building a welfare system that has massive unfunded liabilities, and the only way to maintain these services is to have a population that is increasing at a rapid rate. Now, being that the birth rate in many countries is as low as 1.2 children per couple the population of Europe is shrinking at a rapid rate, so the only way to get this population growth is to have immigration set at a rate which is so rapid that the standards have to be set very low to make it possible.
Now, personally I would suggest having immigration at a more reasonable level where you could attract the best and the brightest who have the highest probability of becomming a well adjusted productive member of your society; and telling people that the promises made by previous politicians for cradle to grave safety nets were not something that could be delivered.
