Are you very afraid? 3D-printed guns are coming. "Virtually undetectable!" shrieked CNN. "This changes the safety of Americans forever!" shrieked MSNBC. Does it? Six years ago, a company called Defense Distributed posted blueprints for 3D-printed guns on the web. The Obama State Department said that violated the Arms Control Act because allowing foreigners to see them is equivalent to exporting a missile launcher, and that's illegal. Defense Distributed withdrew the blueprints. Gun control advocates were relieved. "We have enough guns in this country already," Massachusetts legislator David Linsky tells me in my new video about 3D-printed guns. But this debate...