I am glad to see Ross explicitly lay out in his gracious rejoinder what he takes the alternative to the liberal moral baseline to be:
I suppose I prefer to think that constitutionalism and Judeo-Christian ethics are the moral baseline where government action is concerned. That is, I believe that the government of the United States should strive to “form a more perfect union, establish justice, insure domestic tranquility, provide for the common defense, promote the general welfare, and secure the blessings of liberty to ourselves and our posterity,” and do so without trampling on any of the liberties enumerated in the Constitution; at the same time, I would prefer that America's leaders pursue policies that are broadly consonant with the Judeo-Christian tradition. (No wars of aggression, for instance.) And I'm pretty sure that “unrestricted voluntary cooperation between human beings” isn't a liberty that the Constitution protects, since the Congress is explicitly granted the power to regulate both interstate and international commerce.
Fair enough, though I don't think specifically Judeo-Christian ethics are an acceptable baseline in a pluralistic society with tens of millions of citizens who do not accept the authority of that ethical tradition. That said, observing the principle of equal liberty (i.e., “that every man may claim the fullest liberty to exercise his faculties compatible with the possession of like liberty to every other man”) with regard to trade in labor is also perfectly consonant with both the Judeo-Christian tradition and the U.S. Constitution. So Ross's baseline seems to me largely irrelevant to his restrictionism, other than not obviously ruling it out. And, as a moral matter, it does nothing to establish what I see as his nationalism: the preference for the well-being of co-citizens over non-citizens, or the preference for reductions in inequality among citizens over even larger reductions of inequality between citizens and non-citizens.
The ultimate reason to endorse liberal principles is that adherence to them produces conditions under which human beings are most likely to thrive (according to the broadest variety of different conceptions of thriving). Even from a nationalist point of view, it is necessary to justify deviations from the principles that are most likely to improve the welfare of the nation's citizens. The argument Ross had offered seemed to be based on the idea that, although de facto not-completely-restricted trade in labor with Mexican workers likely produces net benefits for the nation, these benefits come at the expense of some of the least well-off citizens. The unarticulated argument, I take it, is that certain patterns of material holdings are, for one reason or another, in the interest of the nation, and so that it may be morally legitimate to restrict the liberties of all citizens, and reduce the average national material well-being, so that less well-off citizens may be made better off (or not worse off).
Even if we hold fixed nationalist assumptions, this line of thinking is unconvincing. If we're worried about patterns of material holdings, then we could, alternatively, not further restrict the freedom of citizens to trade in labor with migrant workers, go ahead and realize the economic surplus, and then reallocate some portion of the surplus to achieve the desired pattern of holdings. This produces a gain all around — even if we don't take the welfare of migrant workers into account — and without restricting the liberty of citizens to cooperate with others to mutual advantage. So it is hard to see how what I called a “Rawlsian nationalist” worried about the national pattern of income and holdings could rationally use this worry as a lever for restrictions on the inflow of foreign workers.
I appreciate Ross's meditation on the relationship between Christianity and immigration policy (I think Christianity, which sees all souls as having equal value under the eyes of God, is pretty flatly incompatible with all but the most tepid nationalisms, but nobody's going to take my heathen word for it) which I think identifies one of the chief issue of contention between us.
There are all sorts of variables that the government of a Christian society should weigh when deciding how many migrants to admit, chief among them the effect of migration on civil peace and political stability, both of which are taken somewhat for granted in contemporary America but which have historically been rather fragile things. How to weigh these variables is a point on which intelligent people, Christian and otherwise, can disagree.
I would say we are a society containing a large majority of Christians, not a Christian society, but I agree that “civil peace and political stability” are at the heart of the issue. Statist liberals often worry about the destabilizing effects of income inequality. Statist conservatives often worry about the destabilizing effects of cultural change. Ross evidently worries about both, which puts him at odds with cosmopolitan dynamism on two separate fronts. In this sense, I think Ross's concerns about eroding American national identity and nation-level economic inequality are of a piece. But I think the actual evidence of destabilization, either from national economic inequality or from immigrant-led social change, is very scant. I, for one, think we are in a period of both rapidly evolving American cultural identity and increasing social, political, and economic stability. Ross is right that this is an argument worth having, and I think we're starting to have it, which is good. Let the data soar!
But, I've got to insist, the arguments over (a) whether the existence of political boundaries and co-citizenship is a conversation-stopper when it comes to matters of justice, and (b) over the amount of moral consideration to give to the well-being of non-citizens when it comes to assessing the costs and benefits of trade, are also worth having (i.e., worth not avoiding.)
Reihan has also written a long, meaty rejoinder (and who doesn't take pleasure in Reihan's long, meaty rejoinder?). I'll get to that a bit later when I get a chance.