In the New York City of the 1940s, an Irish cop beating up an Italian (any Italian, not just gangsters), was an acceptable prejudice.

I know I'm gonna get in trouble for this, but I'll say it anyway: Irish cops have always been a clannish and exceptionally rude, vulgar and racist bunch here in New York. They came here with the benefit of speaking the language, giving them the upper hand when it came to city jobs. They always held it over the heads of other Euro groups.