Boy, do I have a book for you.
It's called Mayflower, by Nathaniel Philbrick. I'm just now getting to the way that summary executions informed by fear and rage during wartime made enemies of people who were formerly neutral or friendly.
Those who are ignorant of history are doomed to repeat it. One cannot school people in civilization by the practice of barbarism, no matter how righteous one feels about one's actions.