Eleven years ago, like every citizen elected to serve in Congress or any person appointed to any federal position, I swore an oath to “support and defend the Constitution of the United States against all enemies foreign and domestic.” I’ve always thought it significant that the Founders included domestic enemies in that oath of office. They thought liberty was as much at risk from threats within our borders as from outside, and French political thinker and historian Alexis de Tocqueville agreed with that warning. In the immediate aftermath of the terrorist attacks of Sept. 11, 2001, the greatest threat to...