The trial of seven animal rights activists under domestic terrorism laws focuses attention on a threat which law enforcement officials say has become greater than that of the Ku Klux Klan, neo-Nazis, and right-wing militias. Defendants in the federal trial in New Jersey, which has just begun and is expected to last into August, are charged with conspiracy and interstate stalking involving the vandalism and harassment of employees of labs that use animals to test drugs and chemicals. Officials say this is part of a growing trend that in recent years has included more than 1,200 incidents of arson, bombings,...