A LOT OF PEOPLE are in a lather about "Soap."the forthcoming ABC-TV situation comedy that is said to be obsessed with sexual themes. Although the network has toned down the first two episodes, a few ABC affiliates - including WJZ-TV in Baltimore - have refused to air them. Now "Soap" is also under attack from religious groups concerned about the trend toward more sex-oriented television shows. Some of these groups, notably the Christian Life Commission of the Southern Baptist Convention, have been putting pressure on advertisers with barrages of letters and hints about boycotts of products sold on "Soap." The controversy has caused some major companies to shy away from the show.

Well, we haven't seen "Soap" - it won't go on the air until Sept. 13 - and so we don't know if it's racy or funny, raunchy or worthwhile, or all of those things. But neither do a lot of the show's critics, who haven't seen it either but have set themselves up as authorities on the subject anyway. And that's just the point about a lot of these protests. Second-hand reports or published summaries may be only guide viewers have for deciding whether to tune in. But these sketchy critiques are skimpy grounds for a judgment that the program should not be aired at all.

Nonetheless, more and more groups with fervent views of one kind or another have been launching preemptive assaults on programs they consider objectionable by putting pressure on television stations, networks and advertisers. Last year CBS-TV got a flood of mail against a documentary on hunting - months before the program was shown. Such attacks are disturbing, and not just because they come from groups with a special focus and a particular ax to grind. They also are a form of censorship of the airwaves that denies most viewers a chance to decide for themselves whether controversial programs are interesting, tasteful or fair. What's worrisome is that commercial television - which has been innovating gingerly - may buckle under this pressure and retreat still further into blandness and inanity, without giving most viewers a chance to be heard.

Some critics of "Soap" are taking a more reasonable approach. The National Council of Churches, the United Church of Christ, the United Methodist Church and the National Council of Catholic Bishops are urging their member congregations to watch the show's first episodes and then tell locall stations if they think the show is inappropriate or should be shown later at night. Ironically, that may plump up the ratings for the first few weeks. Even more ironically, so may the publicity generated by the protests.

We wonder whether those who are doing the loudest shouting - without benefit of a preview - have thought about that. In any case it says something about their case against "Soap" that they are not prepared to allow the viewer's reponse to be the final test.