Over the weekend, authorities arrested 39-year-old Chad Castagana on suspicion of sending threatening letters to media outlets and the homes of several public figures including "Countdown" host Keith Olbermann. On Tuesday, Olbermann spoke to Radar Online senior writer John Cook who has been covering the story. Cook said Castagana appeared to be admirers of conservative pundits Ann Coulter, Michelle Malkin and Laura Ingraham. "Ann Coulter and Malkin...sort of present a kind of rhetorical world view where they have their troops out there," Cook said, "and I think he thought of himself as one of their troops and wanted to live...