In the Overture, prior to Act One, Miller provides an overview of Reverend Parris as well as an exposition of Salem and what life was like. The town of Salem was more like what modern readers would call a village. Salem was a newly established village; only about forty years old. From the perspective of the European world, Salem was a relatively uncivilized land filled with religious zealots:
To the European world the whole province was a barbaric frontier inhabited by a sect of fanatics who, nevertheless, were shipping out products of slowly increasing quantity and value.
These Puritans were part of a migration of those who fled England to avoid religious persecution. Hypocritically, this group's own religious fanaticism led them to persecute others as well. And this is what led to the Salem Witch Trials. Keep in mind that this play is loosely based on historical fact. Miller makes note of this in the expositions and the overture.
Historically speaking, the Puritan Movement rose out of the Protestant Reformation. The group of Puritans who first went to America (on the Mayflower) separated from the Anglican Church of England. So, in addition to the notion that Europeans viewed these separatists as fanatics, there was some hostility (from those of the Anglican Church and certainly from Roman Catholics authorities) about their separation and migration to the New World.
However, also note that this was part of European (namely English) expansion, so the Europeans involved in such enterprises might have also regarded those in the New World as pioneers; at least as long as these pioneers continued to ship out "products of slowly increasing quantity and value."