A large proportion of the people I know who fulminate about "illegal immigration" had relatives who came here under at best cattle-call circumstances, if not outright "illegal" ones themselves. A nontrivial portion of my generation's Boston Irish grandmothers, great-grandmothers, and great-great-grandmothers did not necessarily have all their papers in order; it's just far enough back to somehow legitimate it.

Also, they're white, and that plays a role--even today there's a surprising number of undocumented Irish immigrants to the United States but nobody's out there asking for reactionary measures to that.

It's not always racism...but it is mostly ladder-pulling, and economically unrealistic ladder-pulling at that. (Ask a farmer.)