Linda Ellerbee, for decades, has been turning out clear, crisp, important television on an endless array of topics – sometimes for adults, and, for quite a long time now, for kids. That doesn’t mean she and her producers (in this case, Martin Toub) pander or simplify. Take tonight’s new Nick News special, for example: It interviews kids who have lived through periods when their parents were physically abusing one another. Sometimes, and this is one of those times, just broachin