There are no social structures able to serve waves of immigrants since they have been designed for the needs of the existing population. So there must be limits and controls on immigration till the state structures are ready and adequate for all.
Immigrants ,as they are willing to work more for less, are preferred by employers and thus create real wage unemployment among local population.
Immigrants drain local economies because of the frequent uninsured labor and capital export.
History has shown that immigration without limits has failed, as in the case of Sweden.
Even if we accept the free movement of people as an ideal, the transitional state must be considered, because it may have adverse effects such as the rise of xenophobia and racism.
There is no need for restrictive integration policies if there are policies that encourage multiculturalism.
The real wage unemployment can be confronted by establishing minimum wages and checks for black labor.
Research shows that ,in general, immigrants contribute more to taxes and social security than they receive in benefits.
As ideal as multiculturalism may sound, integration of migrants is necessary to some extent in order to attain a harmonious coexistence and cooperation,
otherwise migrants may create parallel societies and become a foreign body in society.
Multiculturalism without integration has failed in many european countries and this is proved by the confessions of the countries' leaders,
the rise of the extreme right in Europe and the terrorist activities.
In practice there may be excess manpower at a given time in a market mainly due to the bad synchronization of the increasing demand and the increasing supply. If the theory that nobody is redudant in a market was true , we wouldn't have unemployment in practice.
It is neither logical nor acceptable to sacrifice workers' conquests and rights because of immigrants..
Multiculturalism has succeeded in many countries such as the USA, Canada and Australia.
Multiculturalism can succeed in countries with loose national affinity but cannot be considered as a panacea.