'Conservative vs. liberal'
Conservatives either distrust or the nicer ones are sceptical about new things and new people. They want to preserve culture and traditions. Their opposition to immigration is not surprising. Assertions such as “those strangers won’t fit in” or “ Our country could change in terrible ways if we let Irish Catholics/Pakistanis Muslims in” pepper their speeches.
By contrast, liberals find this cultural conservatism hard to understand and also morally repugnant. They consider conservative pronouncements of cultural superiority and disdain for people from other cultures invidious and offensive to the core liberal principle of universal respect for human dignity.
However, liberals turn out to be just as bad as the conservatives, when it comes to immigration controls; due to their commitment to the realistic utopia of a decent society with a safety net for all citizens. After all, one cannot expect to build such a welfare state in which everyone in the society has the right to health care, education, unemployment protection, disability support and pensions, without building up a wall to keep some people out.
The welfare state has the financial characteristics of an insurance system. This means that the economics only works for the people it was designed for - i.e. us. We have to keep out poor people who can’t afford to pay the premiums our standards require.
Secondly, the legitimacy of a welfare system depends on the perception of fairness or reciprocity. I pay taxes to protect people like me from suffering misfortune. I have to believe that the people asking for help would have contributed like I do except for their bad luck. The legitimacy of these taxes are undermined if the taxes are all taken from people like me, but the benefits go to people who seem to have chosen to become the recipients. Therefore, legitimacy requires that welfare systems be designed as a closed system so people cannot choose between them, on the basis of which one gives them more benefits.
Thirdly, the standards that we consider the minimum of human decency cannot be extended to everyone because we can’t afford that. However, unless we build a wall, we will basically be committing ourselves to such a universal welfare system to which anyone may apply. We therefore face a choice; we can make a status distinction within our borders between ‘real citizens’ with welfare rights, and non-citizens with no rights, which means that there will be possibly millions of people living and working alongside us whose children cannot afford to go to school, or hospital, etc. That would be unpalatable and the proper name for it is apartheid. The alternative is providing universal standards within our society but keeping everyone else out, which is what all liberal states have more or less chosen.
Finally there is naked self-interest. When we think about the welfare state, we normally think of it in terms of helping the poorest and most vulnerable members of our society through direct welfare benefits, such as redistribution, and the advantages to all from government organised goods like public education, transport, and public health systems (public goods). However in reality the middle-class people in formal employment receive an enormous indirect benefit through wage control. The biggest benefit, provided by the welfare states to their citizens, comes in their regular pay packets as the premium for not having to compete with poor foreigners who would willingly do your job for less. As Gary Becker pointed out in The Economics of Discrimination ↑ , segregated labour markets - whether by citizenship, or gender or race as in the past, are good for the favoured workers, but bad for those kept out, for employers, and for consumers. Indeed, immigration controls are estimated to cost the world economy as a whole tens of trillions of dollars - as much as 50-150% of global GDP ↑ ↑ - in lost productivity. This underlying selfish concern to protect our privileged status is rationalised and moralised in the rhetoric of foreigners stealing our jobs (the same rhetoric previously applied to women and racial minorities).
Overall, It is not surprising that the political success of the liberal project - as seen in the growth of welfare states in scale and ambition through the twentieth century - was accompanied by the growth of immigration controls. The viability, legitimacy, and decency of any welfare state depends upon controlling membership to the society it is created to serve. That's what a real social contract looks like. Liberals are always criticising the racist motivations for and practical inhumanity of the immigration controls demanded by conservatives, but their objections are superficial. Conservative orthodoxy allows liberals to get away with the hypocrisy of depending on immigration controls while pretending that they are against them.