(FORTUNE Magazine) – Look in any sizable dictionary and you will find ''unmentionables'' as a synonym for ''underwear.'' That quaint locution is sitting there because there actually was a time when genteel folks could not allude in company to anything as sordid as somebody's union suit, and at politer levels even ''trousers'' was held not fit to be uttered aloud. Today, of course, people not only mention underwear in public but frequently take it off right there on the stage, frontally and otherwise, and it is beginning to look as though the only taboos our grandchildren will be able to laugh at are the political ones. For example, they will have trouble understanding why it was considered socially unacceptable back there in 1986 for the country's media stars to tell their word processors that the African National Congress (ANC) was basically run by the Communists. The possibility that some kind of taboo is affecting American reporting about this organization suddenly hit us on March 7, as did the insight that such inhibitions would be an important matter. Among Americans critical of apartheid -- which essentially means all educated Americans -- the ANC is emerging as the most popular alternative to the South African government. Although the organization is illegal in South Africa, and its most popular figure, Nelson Mandela, has been imprisoned for two decades, it is generally assumed that the ANC would win a landslide victory in any one-man-one-vote election in the country. Presumably no such election will take place soon; still, ANC rule sometime down the road looks a lot more plausible today than it did a few years ago, so the organization's relationship to the Communists is plainly something we ought to be clear about. On March 7 the Washington Post ran a long interview, datelined Lusaka (in Zambia), with ANC president Oliver Tambo, and at one point the reporter asked Tambo about allegations that the Congress is controlled from Moscow. Quoted answer: ''Yes, we do have some Communists on our executive, I have never counted how many, but they all owe their primary allegiance to the ANC and that's all that matters to me.'' Given the vaunted tenacity of Post reporters even when not going after American Presidents, it seemed odd that a scribe who had traveled all the way to Lusaka would let Tambo get away with that line about not counting. Equally dispiriting to the present reader that day was a New York Times editorial note, which derided the South African government for assuming that black African rule would inevitably be a disaster. If the Times meant to assert that au contraire black rule in South Africa figured to be democratic, then the paper should also have dealt with the Communist angle. Based on a semi-exhaustive search in Nexis, still the king of electronic databases, we sense that the Times has been running from this angle for years. So what does anybody know about the role of the Communists in the ANC? The organization is run by a 30-man National Executive Committee. If you ask various spokesmen for the South African government how many of the 30 are also members of the South African Communist party (SACP), they will say 19. However, students of South Africa who look disinterested generally put the figure lower. Africa Notes, a scholarly publication issued by the African Studies Program at Georgetown's Center for Strategic and International Studies, said in its January 31 issue that SACP members made up ''half'' of the executive committee. One committee member who plainly has a lot of clout is Joe Slovo, a Lithuanian-born Communist, believed by some knowledgeable South Africans to be a KGB officer, who directs ANC military operations; it is undisputed that the organization's weaponry comes from the East Bloc. The ANC sent a delegation to the recent Soviet Party Congress in Moscow. Tambo himself is not among the Communists on the executive committee; however, he has told reporters in the past that he views Castro's Cuba as a model for South Africa to follow. So why, we keep asking, don't these significant details figure prominently in the extensive coverage now being given the ANC? Is it really too complicated for the median media mogul to be against both apartheid and Communism? And must we really change the meaning of ''unmentionables''?