For journalists, hate mail comes with the territory. And it can come at any moment, with critics instantly shooting off emails when someone ticks them off on a blog or on the air. Fox News host Greta Van Susteren has surely received audience complaints before — but a recent email exchange irked her enough to take issue with it on her own blog. And in a move that Fox executives probably would have tried to discourage had they been consulted, Van Susteren also urged her blog readers to weigh in on the central point raised by her correspondent: that she...