This strain of ugly nativism goes back to the arrival of the Famine Irish and French Canadians in the 18th & 19th centuries. The Know-Nothing Party used the Catholicism of the refugees to stoke hatred and gain political power. It's disgusting to hear from the mouths of otherwise sensible people.

The excellent book Hard Times, Hard Men: Maine and the Irish 1830-1860 by James H Mundy is an excellent resource on both the history of the Irish in Maine and the history of how cynically the wealthy (often themselves transplants from Mass & points south) have instigated, fed, and used this nativism to divide the working class of Maine against itself, lowering wages and increasing repression to the detriment of everyone but the rich.