system
A chat on subreddit /r/NoStupidQuestions
human
Of Italian descent here, from the tristate area, so what i was taught growing up by my irish-hating grandfather (who married a red headed, green eyed Irish woman) was that the Irish gravitated towards law enforcement because they were the only group of immigrants who arrived mostly already at least having a decent knowledge of the language. This allowed them to largely become "in charge" of the major north east cities rather quickly. 

Also the reason why catholic churches in the old cities up north were based on ethnicity. By the time the Italians, polish, Lithuanians, etc arrived en masse, the Irish were already in control of the American church hierarchy. Even to this day, most catholic bishops east of the Mississippi are Irish, with german bishops in the major Midwest cities.

Edit: my grandfather got beat up by Irish cops more than once when he was a young hood in the 30s. Sooooo to say his opinion may have been biased is an understatement.
gpt
I wonder what your grandfather’s teenage self would think about policing today compared to then? Is an occasional roughing up by cops “straightening out a troublemaker” worse or better than institutional prosecution where cops just arrest everyone and toss them into the system and teenagers get a record that dogs them for life?

(Not that it matters I suppose; It is what it is and just a differ kind of suck to be endured until society gets its shit together.)