The use of signals intelligence to monitor communications via phones, wire, radio, satellites and now the Internet has been the NSA’s bread-and-butter function from its creation in 1952 through the Korean War, Cold War, Vietnam and this war against homicidal Islamic fundamentalists. The agency has had intelligence failures, but there’s no evidence of routinely ruining U.S. citizens. The record should count for something.

What is at issue in this controversy is one’s understanding of the nature of threat, from terrorism to local muggers. Across the broad swath of the American population, most people think threats are a reality and want protection from them. That every town in the U.S. has a police force reveals a consensus about flawed humanity. But on the left and right edges of U.S. politics, the imminence of threat is always a secondary concern.

For liberals, disbelievers in evil, no threat is ever as bad as conservatives say it is, whether Churchill warning about Hitler in the 1930s, Reagan about the need for missile defenses, or U.S. street crime. When Rudolph Giuliani sought to bring New York’s crime wave under control, the left called him Rudolph Mussolini, and they meant it.

Libertarian objections are more principled, but like the left, they undersell the effort and achievements of a democracy across 200 years to build durable legal protections for individual citizens—from abuse and from danger.