> You’re going against commonly understood facts here.

Only because of the deep inroads that views such as those of Ignatiev have made into American popular psyche in the last 20–30 years.

> So you provide a citation please that Irish people weren’t treated in such a way

Arnesen, E. (2001). Whiteness and the Historians’ Imagination. International Labor and Working-Class History, 60, 3–32. https://library.fes.de/libalt/journals/swetsfulltext/1489521...

> ...The historians of whiteness are on firm ground when, building on the substantial body of scholarship in American immigration and political history, they reiterate the well-chronicled point that many Irish workers responded enthusiastically to the calls for white supremacy, which in this case is defined as a support for slavery and other political measures designed to subordinate African Americans and participation in anti-black mobs in workplaces and communities. They are on thin ice, however, when they draw from this the conclusion that the Irish were not white but, in embracing white supremacy, eventually became so. The former point is hardly a controversial one in American historiography; the latter is the invention of whiteness scholars.

> Upon close inspection, whiteness scholars’ assertions of Irish non-whiteness rest largely upon their conflation of racialization and the category of whiteness. For Ignatiev and Roediger, the increased popularity of the “racialization of the Irish”—the tendency to see the Irish as a distinct and inferior race—is equated with their exclusion from “whiteness” itself. The two, however, are by no means equivalent. Matthew Jacobson’s Whiteness of a Different Color becomes relevant here. One need hardly accept Jacobson’s assertion that the Famine Migration “announced a new era in the meaning of whiteness in the United States”—what he calls the “fracturing of monolithic whiteness” or “variegated whiteness”—to appreciate the grounding of his arguments in the contours of mid-nineteenth-century scientific racism. Jacobson insists that racial science produced, and American culture popularized, the notion of an “increasing fragmentation and hierarchical ordering of distinct white races.” The Irish become the Celtic race, but it is a white, if inferior white, race. Although Jacobson undercuts his own contribution by concentrating on what he sees as “vicissitudes” of whiteness and by repeatedly translating a rich and complex language of race into the narrow idiom of whiteness, his formulation, if taken at its face value, can effectively dispatch the “how the Irish became white” question, replacing it with “how immigrants became racialized.”

There is no question that Irish Catholics were heavily discriminated against in the 19th century US. (I say that as a person of majority Irish Catholic descent myself.) But, almost nobody before the 1990s viewed them as "non-white". Discrimination against them was very often couched in non-racial terms–especially with reference to their religion. Even at times when it became "racialised" in the US, that was in terms of the idea of multiple "white races", and a hierarchical ranking of them – Irish people were never put in the "non-white" category.