Watching the hysterical reaction of the radical left—such as Ruth Marcus of The Washington Post—to Attorney General William Barr’s thoughtful, well-reasoned, important speech at the Federalist Society convention on the constitutional doctrine of the unitary executive is like history repeating itself. Liberals had the same overreaction to then-Attorney General Edwin Meese’s 1985 speech to the American Bar Association on the Constitution and originalism. Only someone as openly partisan and ill-informed as Marcus could possibly claim that a speech explaining the historical basis of the Founders’ views on the importance of a strong executive is “angrily partisan” and “scary.” So what...