FOR almost 10 years, "White Dog" has been a missing movie. Completed in 1982 by filmmaker Samuel Fuller, it has been shown on cable television in the United States and has played theatrically in other countries, earning praise from audiences and critics. But until its recent debut at Film Forum, an adventurous showcase in lower Manhattan, it has never appeared in an American theater - apparently because its own studio, Paramount Pictures, found it too controversial to release.Now that one theater is breaking the taboo, others will probably follow, allowing audiences to decide for themselves whether "White Dog" is a racist melodrama or an uncomfortably accurate look at American racial tensions. Meanwhile, the movie's history is worth pondering for what it reveals about Hollywood's attitude toward the subject of race. The plot of "White Dog," based on a novel by French author Romain Gary, begins when a young woman (Kristy McNichol) accidentally runs over a dog with her car. She nurses him back to health and decides to keep him as a pet, only to discover that he is a so-called white dog - trained by a white racist to attack any black person in sight. Determined to reverse this evil training, she consults an animal expert (Burl Ives) and then a trainer (Paul Winfield) who happens to be African-American himself. Together they undertake a brave experiment, finding out whether the dog's racial fear and hatred can be replaced by a new spirit of trust and cooperation. One feisty canine is hardly the same as all American society, of course, so we are obviously meant to see "White Dog" as a symbolic film, delivering a cautionary message about the destructive effect of racism on whatever it touches. Underlining this, the dialogue takes every opportunity to condemn racism as stupid, vicious, and just plain sick. Given this fact, it is most peculiar that "White Dog" has been kept out of American theaters for the past decade, whether because it seemed a risky "sell" in the early '80s or because of threatened protest from a wary portion of the black community, both of which have been reported as causes for the film's nonrelease when it was first completed. Joined with other evidence - such as the rarity of major productions on any troubling aspects of American race relations - the shelving of "White Dog" reinforces the impression that Hollywood would rather avoid than illuminate race problems, except in cases where real-life harshness has been carefully minimized or altogether hidden away. Call it the "Guess Who's Coming to Dinner" syndrome. This is a pathetically overcautious attitude. Fortunately, it has undergone a significant change in recent years, or movies like Spike Lee's boat-rocking "Jungle Fever" and "Do the Right Thing" would not have a venerable studio like Universal Pictures ushering them onto the screen. This season is bringing a new wave of exciting films by minority-group members, such as John Singleton and Joseph B. Vasquez, and one hopes their success will encourage the white movie establishment - filmmakers, film distributors, and all concerned with motion pictures - to be more venturesome in the future. If this does happen, those involved can follow the trail blazed by Mr. Fuller a decade ago. Not that "White Dog" is a masterpiece, or that it even wants to be. It falls prey to most of Fuller's usual shortcomings: The story is uneven, the dialogue is often clumsy, and Ms. McNichol has her limits as a dramatic actress. The picture also has a blunt physical realism that puts it way off limits for people who think all dog movies should have pretty collies, adorable children, and happy endings. Fuller's storytelling has a passion that never quits, however, and there are times when his habitually hard-hitting cinematic style leaps into high gear - as in a climactic moment when he frames the dog, the hero, and the heroine together in a grimly suspenseful dance of hope, suspicion, and danger. Through it all, moreover, Fuller's hatred of bigotry rings out so loud and clear that it is hard to imagine "White Dog" ever being suppressed in the first place.