CHERRY HILL, N.J. - He railed against the United States, helped scout out military installations for attack, offered to introduce his comrades to an arms dealer, and gave them a list of weapons he could procure, including machine guns and rocket-propelled grenades. These were not the actions of a terrorist, but of a paid FBI informant who helped bring down an alleged plot by six Muslim men to massacre U.S. soldiers at New Jersey's Fort Dix. And those actions have raised questions of whether the government crossed the line and pushed the six men down a path they would not...