Jonathan Anomaly and Filipe Nobre Faria write, [UPDATE: maybe the page was taken down? Google also provided this link, which goes to Page Not Found]
we argue that liberalism is unsustainable – that recent trends toward low social trust, inter-group conflict, and falling fertility stem from liberal institutions and the social norms they tend to produce. While liberal institutions may not be solely responsible for these problems, they are ill-equipped to address them effectively. Liberalism is an evolutionary dead end, even if it fosters opportunities for wealth and innovation in the short run.
Liberals treat freedom of movement as a moral default. The core liberal commitment to openness – to the free movement of people [and] capital – tends to break down borders, and incentivize companies and political parties to import far more immigrants than citizens of liberal democracies want.
I think of this in terms of the model of “games with three layers.” The individual and the small group play a game against one another. The small group has social norms that every member knows. Individuals may find themselves in situations in which a cheater prospers. That is, breaking the group’s norms can be good for the individual.
To deter cheating, the group must enforce its norms. Norms are enforced using gossip, informal reward and punishment, and loyalty tests.
The small group and the larger society play a game against one another. The larger society forces the group to comply with its written rules. It uses formal systems of rewards and punishments.
The liberal principle is that everyone should comply with the same written rules. Compliance with the formal rules is a necessary and sufficient condition for the society to remain cohesive.
A group might have norms that conflict with a liberal society’s written rules. For example, a clan might decide to discriminate against people outside of the clan, rather than treat everyone the same.
When people first immigrate, they are likely to be drawn to a group of similar immigrants. Until they become comfortable in the larger society, they will find it easier to comply with small group norms than to follow the written rules of a liberal society. In the United States, our history is that eventually within a few generations immigrants have assimilated into the larger society. Immigrants have learned to play by the rules that allow different clans to live in harmony, rather than let clan loyalty supersede the rules that are meant for everyone.
Will assimilation take place if the number of immigrants is large relative to the overall population? That is the important empirical question. If immigrants fail to assimilate, then there will be a large sub-population that does not conform to the formal rules.
The authors raise another issue.
current trends continue, Muslims from Africa and the Middle East will become the majority population in many European countries over the next century.
Will Muslims resist assimilation into liberal societies? That is another empirical question. There certainly are some Muslims who come to hate the societies of their adopted countries. The challenge is to keep that segment of Muslim immigrants as small and insignificant as possible.
In my view the immigrants are less the problem in the US than the coastal elites who favor them. In Europe I think it’s different. Immigration there is going to cause a lot more problems.
I don't think assimilation is the primary question, although it is a big one. I think the primary question is whether or not we are enforcing our own written rules and norms, and that is upstream of what immigrants are assimilating to.
Europe maybe a bit different, although the UK examples make me wonder, but in the US we have in many places seemingly given up on enforcing property laws on even our own citizens, for example. Even if we took immigration down to zero we would still have rampant theft and destruction of property, not to mention the violence in cities like Chicago. The underclass criminal culture has thus been not only tolerated but encouraged, not only through media but also government tolerance and active political encouragement, and we are seeing the results.
Now add immigrants back in, and ask "Into which local culture do they assimilate, the middle class who value hard work, education and respect for others' property, or the underclass who see work as a sucker's game and a life of crime as high status?" Then ask the same about their teenage boys.
I would say our primary problems are home grown, and immigration only makes it a bit worse.