“Bad TV,” in this case, doesn’t mean reality television, which has a kind of integrity in its shamelessness, but old-style idiot-box TV like The Man From U.N.C.L.E., Gilligan’s Island, and Dynasty. And as the much-ballyhooed age of Peak TV runs on, argues Paula Marantz Cohen, some of the most insidious traits of Bad TV are creeping into what ought to be high-quality material.