Neither of these arguments is wholly convincing. First let’s concede that it is insensible in almost all non-figurative contexts to describe a person as “illegal,” much as it is insensible in most contexts to describe a rock as “aroused” or a bicycle as “Presbyterian.” But it hardly satisfies Ockham or the principle of charity to conclude that those who use “illegal immigrants” are thus speaking nonsense. The likelier explanation is that surface grammar obscures what’s really going on in these elocutions — namely that “illegal” describes not people but people-engaged-in-an-activity, namely people-as-immigrants. And in doing this, it captures an informative, relevant distinction. “Illegal gambler” and “illegal distiller” don’t imply that the gambler and distiller in question are themselves illegal, just engaged in an illegal pursuit. It’s an illicit move to interpret those phrases otherwise, akin to my taking someone who calls me a “bad baseball player” to be calling me bad in every way, bad full-stop.
And to address the response that inevitably comes — that somehow “illegal immigrant” sullies all immigrants — “illegal gambler” and “illegal distiller” don’t imply that all gambling or distilling is illegal either.
So what about the purely normative argument, that referring to a group of persons as “illegal immigrants” unfairly “labels” them? Again, let’s concede that lots of people do use the phrase to express disapproval of its referents. There are still two problems with changing the phrase. The first is that, once you acknowledge that “illegal immigrant” has real descriptive content, changing it amounts to euphemizing, and whatever word or phrase is slated to take its place will be subject to what has been called “euphemism inflation.” Think of the transitions from “idiot” to “mentally retarded” to “cognitively disabled,” and so on. Each iteration is a euphemism, meant to preserve descriptive content while jettisoning the derogatory connotations. But over time, the euphemism itself absorbs those negative connotations, and thus has a shelf life, requiring another, and often more cumbersome and/or less descriptive euphemism to replace it. (There are a thousand other examples of this phenomenon. The history of names for the room in which humans defecate could be an entire column.)
“Fine,” you might say, “but that’s no argument against using up the next euphemism and replacing it when the time comes — there are plenty of words in the English language.” This brings me to the second argument against euphemizing: Illegal immigration is bad! Even if you favor broad immigration reform or, hell, open borders, you presumably still oppose lawbreaking as such. This makes the shift to euphemistic language here unlike the shift from “Negro” to “black.” There really is nothing wrong with being black, and a move away from a word that implied there is something wrong with being black is salutary. But most reasonable people agree there is something wrong with illegal immigration, and no purely terminological change is going to wash away that normative judgment. The whole point of unkind descriptors (“bastard,” to take one at random), and of the language of admonishment in general, is to discourage unwanted behavior (like out-of-wedlock pregnancy), if only at the margins.
And I’ll admit, while I think “illegal immigrant” is perfectly reputable and descriptively adequate, there are various alternatives that have certain advantages. I’d be fine, for instance, with something like “unlawful residents,” because immigration offenses often fall short of full-on criminality, and focusing on residency avoids the ambiguities of “immigrant” described above. But if we’re going to change the way we talk about this stuff, the motive should be clarity. It shouldn’t be to win a substantive political argument by literally changing the terms of the debate.