A federal judge in Manhattan on Thursday refused to let thousands of Detroit homeowners sue Morgan Stanley as a group for allegedly pushing a subprime lender into making risky loans they could not afford. U.S. District Judge Valerie Caproni said her decision was likely “a death knell” for the lawsuit and that an appeal may be appropriate, but that the plaintiffs’ claims were too varied to be addressed in a single class action. The complaint was originally filed in October 2012 by the American Civil Liberties Union, in what that group called the first U.S.