Woody Allen comes out four-square against the Frisbee on "The Dick Cavett Show" tonight. "I associate it with the West Coast," he says disdainfully. "It's like a strange, odd, plastic recreational instrument for people who can't really play ball."

No one can intone a phrase like "recreational instrument" and have it speak worlds the way Woody Allen can. Not the same worlds, anyway.

Allen's half-hour chat with Cavett, at 11 p.m. on Channel 26, marks his public television debut - five years late. It was scheduled originally for 1972, when Allen wrote and starred in "The Politics and Humor of Woody Allen," a one-hour film that scared the bejeebers out of public TV officials when they saw it.

The program was withdrawn while lawyers huddled over it as if it were a ticking time bomb that could topple the republic. A documentary, ironically-or-not titled "Come to Florida Before It's Too Late," was aired in its place.

Allen refers to the program on tonight's interview as "a silly little firm . . . and amusing little trifle" and Cavett writes it off as a victim of the Nixon White House and its vendetta against galloping liberalism in public television. No blame for the fiasco is affixed to public TV officials; nor is it suggested that bullies thrive best when they set upon cowards.

Cavett and Allen are friends, and that's probably why Allen agreed to do the show, since he has said repeatedly he will not appear on television for fear it will lessen his box-office draw. But the friendship works against the very interview it made possible; Cavett is obviously reluctant to ask any questions that might irritate or antagonize an old pal, and so the program is essentially a waltz.

Still, it's a chance to watch Allen hem and haw in an amuzing or at least ingratiating manner, and at one point he off-handedly provokes from the icy Cavett one of the loudest laughs Cavett's ever laughed on the air. This is over in a blurt, but it's a pleasure to see Monsieur Sangfroid even momentarily drop his guard.

Actually, the show may be less interview than group therapy for two. When Allen expresses envy of Cavett's prowess at browbeating cab drivers and waiters, when the reminisce about their separate but equal early career struggles, and when Allen marvels at Cavett's zest for hobnobbing with celebrities, you sense insights lurking between the words. Allen emerges as a man who re-channeled his revenge instincts into films and essays sometimes brilliantly as well as cathartically funny.

Cavett became a television personality.

The portrait of Allen may offer nothing really new, though, it is gratifying to hear him praise again the "gossamer touch" demonstrated by Bob Hope in Hope's early films, and it is distressing again to hear Allen reiterate his pledge "to keep myself from acceptance - by the masses." He plans a "very serious dramatic movie" and wants to make "all those decisions counterproductive to my best interest" - and, alas, to those of his audience as well.

But the picture of Cavett gets a bit more complete tonight. Here is a public keeper of the cool who is apparently, off-camera, a feisty, temperamental scrapper. Sometimes you get the feeling Cavett would rather die than let any of his anger, emotionalism, sentimentality or proletarian Midwestern roots surface on the air. The arena of public television seems to have further suppressed rather than liberated such qualities. Dick Cavett may be the one person in TV who should get stoned before he goes on the air.