TONIGHT CBS News will say more emphatically than has ever been said on prime-time network TV that prime-time network TV stinks. "CBS Reports: Don't Touch That Dial!" at 10 on Channel 9, is a breakthrough documentary and a brave one. In looking at how entertainment programs are created and sold to the three television networks, it's funnier, and sadder, than most of the network programs are. And of course a good deal more thought and ingenuity has gone into it.

The program seeks an answer to the Great American Question, "Why is TV so bad?" Correspondent Morley Safer notes during the broadcast that "much of television seems designed to glaze rather than excite our minds" and says up top that the point of the documentary is "to give you a glimpse of how prime-time television works." In concentrating astutely on one specific aspect of television, Safer and producer Julian Krainin do more than afford a glimpse. They offer an instant education in What's Wrong.

Safer asks B. Donald "Bud" Grant, president of CBS Entertainment, if all those "repetitive clone series" are the best the networks can come up with. Grant, who looks like a middle-aged Wimpy, delivers a lulu of an answer: "Frankly, I think I'm constantly amazed that television is as good as it is," he says. And: "I think it's absolutely amazing that television is as good as it is." And: "I think we are in touch with the public." Safer also talks with Brandon Tartikoff, president of NBC Entertainment ("Network interference . . . is a fact of life . . .").

But Safer does not talk with Anthony D. Thomopoulos, president of ABC Entertainment. He doesn't talk with anybody from ABC because ABC executives refused to cooperate with CBS News on this report.

ABC is currently getting whupped by CBS in the prime-time ratings race, and even ABC's once-invincible daytime lineup has begun to wobble. So it looks all the shabbier for ABC to hide from Morley Safer, who to his credit saves his toughest questions for CBS' own Grant.

Why did ABC play chicken? Not one of four ABC spokesmen I asked came up with an answer. Andrew Lack, executive producer of "CBS Reports," said from New York that after weeks of off-camera discussions with Thomopoulos, CBS News was told by an ABC publicist in Los Angeles that no ABC programming executives would consent to on-camera interviews.

On the CBS program, which concentrates on the journeys through bureaucracy of two new fall shows--NBC's "Family Ties" and the CBS "Seven Brides for Seven Brothers," both now hanging on by threads--Safer talks with several TV producers who don't sound all that enthusiastic about the buying and selling process and the way networks dictate how programs must sound and look even before they buy them.

In an excerpt from a speech seen near the beginning of the program, Lee Rich, producer of "Dallas," "The Waltons" and other TV hits, says, "There has to be something wrong with a business that spends so many millions of dollars in the area of development and creates so little acceptable product . . . If you have a marriage that doesn't work, you try to fix it. If you have kids that you're having problems with, you try to do new things. This has been rotten for the last 10 years. Why don't we fix it? The audience shares are eroding. The network structure as we know it is in jeopardy."

Barney Rosenzweig, who tried unsuccessfully to get a network to buy a series called "Modesty Blaise," about a female crime fighter, tells Safer, "The thing I feel bad about is when you make it to their order, and then they reject you . . . I failed by doing what they asked me to do. That's what I feel sick about." Even Fred Silverman, who rode a comet through all three networks, has lost faith. "The problem with television today is the producers and the writers and the directors have been recycled," Silverman tells Safer. "They go from one failure to another. I'm not indicting the networks. I really am indicting the system."

But the best parts of the documentary are not interviews or speeches. Safer and the crew take viewers into privileged sanctums of networking -- lunch at 21 during the program-buying season, with CBS vice president Harvey Shepard being wined and dined by a nest of nervous producers, one of whom orders "a blood transfusion" and "a stomach pump"; the NBC affiliates' convention at which Tartikoff says of the new network lineup being unveiled to station executives, "All across the board there is youth and excitement"; and a New York hotel suite in which David Gerber, the very likable veteran TV producer, sweats out the minutes awaiting word on whether or not CBS is going to spring for his "Seven Brides."

The phone rings. "Wait a while," Gerber says. "This may be my whole life here." Later, after shooting has commenced on the series in northern California, Gerber tells Safer he chose the remote location partly in the hope that network executives would have a hard time finding it.

But the makers of this documentary themselves lucked out in finding Gary Goldberg, producer of "Family Ties" and so relatively new to the business that he has yet to learn the art of saying nothing. He's wonderfully candid about the risks and horrors and potential rewards of producing a prime-time TV series, and he's at his best describing for Safer the buzzwords network executives use to tell producers to hype up their shows.

"For instance," Goldberg says, " 'topspin' is a great network word. They say, 'There's not enough topspin here.' And we say, 'Wait a minute -- what are you talking about?' . . . They say, 'Well, topspin in network terms is something that happens in the scene to propel you into the next scene.' Usually, someone loses a briefcase or something really exciting, and that's the topspin into the next scene."

Goldberg says "heat" means "tension, argument, usually somebody calling somebody a 'fat mother,' or some great thing." He also defines "blow," "hook" and "button," and says, "You will never hear discussions . . . any deeper than that about the writing, about character development and motivation and reality, and truth of the moment. But . . . a show will always have heat, topspin, pipe, hopefully a good button and a hook, and a great blow."

Safer notes that the three networks' shares of the viewing audience are declining. He doesn't talk about cable and pay TV and Pac-Man, but then this report is not called "All About TV." Safer doesn't bring up the current Federal Communications Commission proposal to rescind a longstanding syndication rule, either, but it figures implicitly in this report. The networks engender and buy shows, but are currently forbidden from syndicating them after or during their network runs.

The networks want, and are mounting a monstrously awesome lobbying campaign to secure for themselves, control over the syndication rights and the millions in revenue that entails. What tonight's report says between the lines and between the pictures is that yes, the system needs an overhaul, that there is something rotten about it. What common sense and many decades of American broadcasting suggest is that if the syndication rule is revoked, the system will indeed change. It will get, and this prospect really does boggle even the most frequently boggled mind, worse.