BADNESS IN television can be more readily defended than badness in any other medium. TV has a great excuse: its enormous and helplessly undiscriminating appetite for material.But television also tends to banalize almost everything it touches, a fault that seems to be built right into the medium.

Television can bring good art down and bad art up, so that a lousy theatrical movie like "Airport 1977," when televised, can prove more satisfying - perhaps "better" - than a presigious Laurence Olivier production of "Cat On a Hot Tin Roof" that aims for the stars and falls flat.

While "Airport 1975" was a bad movie that became tolerable television, Olivier's "Cat," taped for TV, really was dynamically bad, in part because it was directed as if the camera were an unwanted intruder, but more so because of its implicit aspirations to Art. This was to be worthwhile television; this was to be cultural uplift.

That's the worst kind of bad TV, the respectable and lofty stuff that pretends TV isn't a ploletarian medium. If you want to see bad television with no redeeming morbid fascination, then you watch "Eleanor and Franklin" - as noble, stuffy, distanced a piece of anti-television as was ever made.

Is such stuff supposed somehow to earn us the right to slum guiltlessly among tThe Hollywood Squares"?In fact, "The Hollywood Squares" makes better use of TV's peculiar visual personality than "Eleanor and Frnaklin" does. The idea of dividing a TV screen into a tictac-toe board with a celebrity in each hole is really rather inspired, commercially and visually; it's one of the true brainstorm formats in the history of television.

The idea of filming an arch and respectful historical drama about lofty figures trated with velvet gloves is not only inspired, it is not an idea at all, and the result is not television but a kind of numbing audio-visual pop textbook.

Bad television is not "The Gong Show," which is itself a playful celebration of badness as goodness and of television's capacity to ennoble amateurism as no other medium ever could - the element in TV that makes possible all the "Eyewitness News" shows on local stations. Bad television is The Shirley. McLaine SPecial, "Where Do We Go From Here?," an excruciating spasm of cutesy pseudo-liberalism packaged in slcik electronic plastic and aggressively antihuman.

A televised bad movie is translated into something else, perhaps even a good television program. A mediocre film, even one made for television, can become something else too. This was the case with "Roots," which became, when watched by the largest audience in history, the kind of nearly unanimous shared moment that only television can make possible.

Bad television can be lookily riveting in a way that bad movies and bad plays cannot. The infamous Mary Tyler Moore special, "Mary's Incredible Dream," was not just wildly terrible, it was wonderfully terrible; you coudl forsake "Eleanor and Franklin" without a moment's pause, but "Mary's Incredible Dream" proved thoroughly seductive.

In somewhat the same way, what may have been the most ill-conceived, tasteless and poorly executed network special in history, "Evil Knievel's Death Defiers," became fascinating as it progressed from the merely awful to the sublimely, unimaginably offensive. The crazy thingabout much of bad television is that it can be irresistibly appalling.