JACK VALENTI IS A SHREWD TACTICIAN, but the scheme to impose a version of the motion picture ratings upon the TV world may be a classic case of overreaching. It became clear last week that the TV industry is close to adapting ratings as a means of harnessing the V-chip to specific criteria — a notion that poses formidable economic and strategic problems for programmers and advertisers alike.It’s appropriate that all this is coming to a head amid the noise and nastiness of the Republican primaries — a campaign that underscores the irreconcilable differences that preoccupy our society. Analyze the oratory about movies and TV and you quickly realize that the politicians really are talking about two different issues. The Pat Buchanans of the world want an S-chip, not a V-chip. They want to banish sex but arm everyone with a gun. Democrats, on the other hand, talk about cutting back on violence, yet usually don’t go into paroxysms of indignation if a character on “Seinfeld” happens to do a riff about masturbation. Thanks in part to Valenti’s political skills, the MPAA has been able to skate around America’s schizoid attitudes toward ratings. Filmmakers quietly mutter about the inequities of a code that applies a PG rating to a rather violent film like “Indiana Jones and the Temple of Doom,” while consigning “Priest” and “A Perfect World” to an R. They also complain that the majors carry more clout in making their appeals to the ratings board than do the smaller distributors. The NC-17 rating has proved to be more a stigma than a protective haven for serious adult fare. Despite all this, no one really stands to gain by making a “federal case” about these supposed inequities. In administering its ratings, the movie industry has accomplished its primary objective of erasing local censorship bodies whose failings and foibles would be vastly more egregious than those of the MPAA. Transfer all of this to TV, however, and major cracks start appearing in the superstructure. No one sits around and counts the maimings or sexual references in a movie, but the landscape is loaded with groups that do just that in TV. The clashing agendas will become all too clear: You’ll be able to shoot as many people as you want on TV at the 8 p.m. hour so long as edgy sitcoms like “Friends” or steamy melodramas like “Melrose Place” are banished to the late evening. AND I DOUBT IF ANY OF THE PROPONENTS of ratings have begun to ponder how to deal with soaps, tab TV or even ordinary news shows. Combine ratings with the V-chip and you get chaotic change in the TV world. As even Valenti concedes, “I don’t know where we’re going on this, and if anybody tells you they know for sure they’re wrong.” Syndicators are scratching their heads, wondering whether reruns of an R-rated show will be banished from the lucrative primetime access period. Programmers are troubled as to how they can hold onto an audience week-to-week if every episode elicits different ratings. One can almost hear the V-chip clicking off “Friends” one week because someone alludes to sexual congress, while the next episode sails through untarnished. Then, too, advertisers, who’ve ducked away from edgy, “NYPD Blue”-type shows until they’ve become successful, will have to decide to run the V-chip gauntlet in search of younger and wealthier demos. In view of all this, why are webs like ABC and especially Fox ready to embrace what could turn out to be a logistical nightmare? Part of the answer is simple politics. Faced with a White House summit on Feb. 29, the pressures have become too intense to ignore. Besides, webs have more important fish to fry — namely the fight against auctioning off the broadcast spectrum. SUDDENLY JACK VALENTI and his ratings seem like a reasonable alternative to facing down agitated lawmakers and a president running for re-election. Hollywood has been there before and learned the value of political expediency. Besides, the only noise one hears against the movie ratings system comes from overseas, where many feel that Hollywood blockbusters are exporting America’s schizophrenia — its films reflect the violent subtext of a sexually repressed society. Now, it would seem, we will be institutionalizing this conflict on the V-chip. I can almost hear TV sets around the U.S. clicking off “Seinfeld” and positively doting on some vivid shootings on the 6 o’clock news. As for me, I’m going to rig my chip to censor out every politician running in every primary. Maybe it even can ax Jerry Springer.