"Mr. Smith Goes to Washington,' where are you now that we need you?"

"Mr. Smith Goes to Washington" -- where are you now when we need you five decades later? TV is finally getting around to social-consciousness drama and the role of the individual in the solution of society's ills. But, as in the case of "Angel City" (CBS, Wednesday, 9-11 p.m., check local listings), although the problem is valid and familiar, the solution is, perhaps, just as frightening as the problem itself.

Ralph (John Walton) Waite brings his salt-of-the-earth indomitable character to this '30s-in-the-'80s melodrama. Paul Winfield offers a beautiful performance in the role of a black migrant worker, grateful to be included in plans of the white Waite (Teeter) family to run a roadside fruit stand in Florida after escaping from their poverty-stricken West Virginia farm -- although Winfield's "Lawsy-Miss-Scarlet" sincerity may be considered an offensive stereotype to some viewers.

Both actors play their stereotypical roles with infinitely believable skill. Not since "The Migrants" several years ago has TV handled the subject with more delicacy and understanding.

All of these people -- and lots more -- have been lured into a migrant-worker "slave labor" camp in northern Florida, run by a rascal of a contractor who keeps them behind barbed wire; charges them to be transported to the cucumber fields; provides them with slave-quarter-like shelter and a bottle of wine a day , for which he over-charges them; uses their own food stamps to feel them; and, in general, makes pre-Emancipation Day slave owners seem like enlightened abolitionits.

Patrick Smith, author of the book "Angel City," on which this proram is based , went to live in such a camp and reported many actual happenings in his novel. Although it sounds like something out of another era, "Angel City" is very much out of today's headlines. And it is a worthwhile subject the Factor-Newland Production Corporation has chosen to dramatize, sensitively if a bit obviously, written by James Lee Barrett and directed straightforwardly by Philip Leacock. CBS is to be congratulated for making so engrossing a prime-time drama out of it.

So why am I complaining? It is so seldom that primetime TV chooses valid topics, treats them intelligently, produces them with skill. Why nitpick?

The answer is this: The solution to the problem is so tinged with dangerous vigilante-ism that much of the enlightenment of the script is nullified. The good guys win -- but they win by fire and violence, by beating up the bad guys and setting fire to their slave camp . . . all illegal.

Mr. Smith (Teeter) doesn't go to Washington (or even Tallahassee) to put an end to the mistreatment of migrant workers. He punches and pistol-whips the culprits and burns down their property. It's the kind of Florida justice we have recently seen in the Miami race riots -- the same kind of mob action that soothes the outraged fires of anger temporarily but in the long run solves very little but the immediate problem. The problems that stem from other, deeper sources remain unsolved.

"Angel City" is a program that needed to be done. The book was probably a book that needed to be written. The problem of misusing migrant laborers is a problem that needed to be handled. And solved.

But by arson?