As with most issues the truth is in the middle and any immigration policy should absolutely demand that any immigrant coming into a country assimilate and fully support our values of equality for all.
First generation migrants tend to be, in most receiving countries, less likely to commit crime than native-born population.
http://www.antoniocasella.eu/nume/Bersani_2012.pdf
They found that immigrant men and women were less criminally active than native-born men and women in regard to self-reported crime, being stopped by the police, being charged with a crime, and having contact with a criminal justice agency. This pattern of lower levels of criminal activity among immigrants compared to the native-born held in models controlling for key background characteristics including a variety of educational, employment, and family history measures.
The problem comes with latter generations, if the receiving country isn’t doing an adequate job at integrating them. If the parents work really long hours, aren’t capable of spending much time with their kids, have trouble to pay kindergarten and have trouble teaching their kids the local language, if the kids are victimized by racist bullying at school, have less means to do well academically and land a good job, and are generally otherized by society, they’re at a larger risk getting alienated and engaging in antisocial behavior and even crime.
So, if you don’t want migration to be a problem, invest in public schooling (including kindergarten), offer classes teaching the local language to adults, empower unions, protect labor, and fight racism.
