Wouldn't it be nice (to quote the Beach Boys) if just once Barbara Walters encountered a captured celebrity at the lowest point in his or her life? And if that poor sap said things to her like, "Oh, Barbara, I don't know what I'm going to do! I had it all together, and now it's all fallen apart. The phone never rings. I have no one special to share my feelings. I can't get a table at Spago to save my soul. I think I'm going to kill myself!"

Barbara would turn three shades of pink. She wouldn't be able to squeeze that person into one of the three or four little personality molds she carries around in a purse that must be the size of Hoover Dam. Tonight, she pushes and prods and pokes and tries to reduce three more guests to shrieking Zeitgeist cliche's. Two of them, Robert Mitchum and Eddie Murphy, escape; the third, Linda Evans, is so eager to be a cliche' she scarcely needs help from faithful old Aunt Blabby at all.

ABC has given the latest "Barbara Walters Special," at 8 tonight on Channel 7, a free-ride time slot, just before the Academy Awards in the East and just after them in the West. This may be because Million Dollar Barbara's ratings haven't been all that dazzling this season. At least it can be safely said that tonight's special is more entertaining, in its maddening way, than the musical revues that usually precede the Oscar show.

And it ends winningly, with Eddie Murphy, of "Saturday Night Live" and "48 Hrs.," making Barbara laugh on the living room floor of his unfurnished Long Island home. Murphy tells viewers they should keep watching "SNL" and boost its ratings or else "I'll break into your house on Saturday night."

Barbara is amazing in one respect. Even as she's stroking and petting her guests--whom she almost invariably characterizes as the victims of unfair publicity by others--she seems incorrigibly abrasive and irritating on the air. So that when in the opening segment she bills and coos to Robert Mitchum, says the rumors of his being "a crusty old grouch" are only to hide the fact that he's "sweet" and "nice," you kind of wish Mitchum would brush her aside like a bad bug, for our sake if not for his.

But he keeps his temper and his dignity during the interview, recorded on a pier in the Caribbean. Mitchum says he always regards large crowds as a potential "lynch mob," that "I don't feel successful," that the longevity of his 42-year marriage may be due to "a lack of imagination" and attributes his success as an actor to the fact that "I work cheap." When he says he feels like a "freak," Barbara, in her most patronizing purr, asks, "After all these years--still the freak?"

Barbara is absolutely flabbergasted at the idea that Robert Mitchum isn't really the way he appears on the screen nor the way some of those other journalists have described him over the years. Imagine!

Next comes Linda Evans, "at 40 more luscious than ever" and "one of television's hottest sex symbols," according to Walters. Evans, like almost every celebrity Barbara has interviewed, went through one a them-there bad spells but then, sweet patootie!, came a dawn and "She learned who Linda Evans really is" (Gee, Marsha Mason just learned who Marsha Mason really is, according to "Entertainment Tonight." What would we do without this information?). For readers of the National Enquirer--and aren't we all, deep down inside or right out there in the open?--Evans discusses with Barbara her feelings toward Bo Derek, who replaced her as the momentary one-and-only of one-time actor John Derek.

Barbara has a humdinger for Evans, the kind of question that begs to be salaciously misunderstood: "What does John Derek do that makes a woman feel so wonderful?" She also asks Evans "Do you think you're beautiful?" and Evans makes such breathtaking declarations as "To me, getting older is a magical experience" and "I've learned a lot about myself." This section of the program, beyond its possible value as instant camp, is incredibly boring.

Eddie Murphy suffers Barbara gladly. He comes across as a gratifyingly level-headed fellow, especially for someone bestowed with fast fame. He says he smoked marijuana only once in his life, and adds, "I'm funny without narcotics. I don't have to sniff cocaine to be funny." He also says, "There's no such thing as a humble entertainer." But when he starts to explain why he doesn't like playing the strident black activist film critic on "Saturday Night Live," one of several characters he created, Barbara cuts him right off and goes on to something else.

If Barbara Walters were a shrink, would she have the worst cure record in history, or the best? Whichever, she would probably be the most successful shrink ever in getting patients to transfer their hostility from anyone else in the world--to her. For that, Barbara Walters, we love you, yes we do. Sort of.