Where, many have asked these last weeks, do the rhetorical fireballs — the raging suspicion and rabid xenophobia — come from? Barring people from our shores, Paul Ryan reminds us, is “not what this country stands for.” Emma Lazarus would have agreed. But while the demonizing may sound un-American, it happens also to be ur-American.

Well before Japanese internment camps, before the Know-Nothing Party, before the Alien and Sedition Acts, New England drew its identity from threats to public safety. We manned the nation’s watchtowers before we were even a nation.

From that earlier set of founding fathers — the men who settled 17th century Massachusetts — came the first dark words about dark powers. No matter that they sailed to these shores in search of religious freedom. Once established, they pulled up the gangplank behind them. The city on a hill was an exclusively Puritan sanctuary. The sense of exceptionalism — “we are surely the Lord’s firstborn in this wilderness,” the Massachusetts minister William Stoughton observed in an influential 1668 address — bound itself up from the start with prejudice. If you are the pure, someone else needs to be impure.

Quakers fared badly. In Boston, Cotton Mather compared them not only to dogs, but to serpents, dragons and vipers. The great young hope of the New England ministry, he sounds as if he would have started a Quaker database if he could have. Banned, exiled, imprisoned, whipped, Quakers were a “leprous” people, their teachings as wholesome as the “juice of toads.”

Baptists and Anglicans fared little better. In 1689, Boston’s Anglicans discovered the windows of their church smashed, “the doors and walls daubed and defiled with dung, and other filth, in the rudest and basest manner imaginable.” The most moderate of Massachusetts men believed in Papist cabals; priests qualified as the radical Muslim clerics of the day. From the pulpit came regular warnings that boatloads of nefarious Irishmen were set to disembark in Boston harbor, to establish Roman Catholicism in New England. ...