Why were Italians discriminated against so harshly in the early twentieth century?

[Kimstu]

Furthermore, as we were discussing in another thread a couple months back, there was a widespread perception among Americans of northern/western European descent that Italians simply didn’t count as “white”:

@Kimstu

Here’s a 1916 industrial relations report illustrating the distinction that many employers of the time took for granted between “white men” and “Italians” :

Mr. Barnes: Now, Mr. Petersen, let us establish a couple of facts so we can go on. All of your men that you employ there that are not Italians, are white men? You employ white men and Italians?

Mr. Petersen: In discharging we employ all Italians, and in loading all white men—all nationalities. […]
Mr. Barnes: Yes; but why do you put the Italians at discharging and the white men at stowing. Are not the white men better for stowing?
Mr. Petersen: Because the Italians are not qualified for it—stowing. […]
Mr. Barnes: So you make a division between the Italians and white men and put the white men to stowing and the Italians to discharging?

This article discusses similar evolution of racial classifications of various groups of Europeans, illustrated by the contemporary quote in the article’s title, “A Slav can live in dirt that would kill a white man”.