In the late 1930s, Nazis and their enablers created a map of Jewish businesses to target and boycott, ultimately leading to the Kristallnacht (“Night of Broken Glass”), a violent pogrom across Germany and Austria, in which thousands of Jewish-owned stores and synagogues were looted and almost 100 Jews were murdered. Kristallnacht was an example of how singling out and demonizing a group of people based on race or religion can lead to violence. Less than a century later, a disturbing new effort called the “Mapping Project,” based in Massachusetts and linked to the movement to boycott Israel, has again singled...