ON WEDNESDAY of this week, on page A9, this newspaper published an ad from an organization that calls itself Accuracy in Media (AIM). The ad accused The Washington Post of "censorship of information that is important to the public and of interest to the readers." AIM describes itself as a "non-profit, non-partisan educational organization, founded to combat inaccuracies and distorted reporting by the major media" and its complaint had to do with the Post's coverage of a panel discussion sponsored by AIM in Washington in November of last year.

It was AIM's view that the Post should have published an account of the conference by United Press International. The UPI account featured criticism of the news media by Lt. Gen. Daniel Graham, former director of the Defense Intelligence Agency, and by Bruce Herschesohn, a former special assistant to President Nixon. Words like "withheld" and "suppressed" were flung loosely about and the ad featured the text of the UPI dispatch with the word "CENSORED" superimposed across it in big, bold type. The ad complained that the Post, while with holding the UPI criticisms of the press,had published a portion of an Associated Press account of the same event "which focused on statements made by two of the 27 speakers at the conference that were favorable to the news media." AIM's point seemed to be that the press in general and the Post in particular are "not eager to publish serious critism of the news media and the way they are doing their job."

To all of which we would reply, in a word - rubbish. In keeping with our occasional practice of discussing (For Your Information) the whys and where-fores of our business, let us elaborate a little. For one things, we count ourselves among the pioneers in the field of journalistic self-criticism. Since 1970, we have had an Ombudsman on this newspaper, and the incumbent, Mr. Charles Seib, is no less ready than his three predecessors to fault the performance of the Post and the press in general in his weekly column appearing Fridays on the opposite page; well over half of the letters to the editor that we print are critical of something or other that appeared - or failed to appear - in the newspaper.

As to the decision to run a portion of an AP account of the AIM conference (rather than the UPI's account, or another wire service account, or an account by one of our own staff correspondents, or nothing at all), just about everything that gets in, or gets left out, of a daily newspaper can be subjected to same sort of post-mortem analysis. Close questions are what news editing is all about - if you accept the simple reality that not everything that everybody thinks is newsworthy can be squeezed into a newspaper in a form that will satisfy every interested party, every day.

So even assuming, for the sake of the argument, that UPI's dispatch was more interesting than AP's the point is that the decision to publish one and not the other has nothing whatsoever to do with "censorship" - which, if our dictionary serves, is a word generally associated with an officil act . And it has nothing to do with "suppression," except as that might be one way to describe the sheer necessity, on a daily basis, of leaving out of the newspaper a high proportion of the material that is available from wire services, news services, and our own correspondents. It has to do simply with the necessary application of an editorial judgment. And the right to exercise news judgment is one thant we think a newspaper is entitled to reserve to itself.

That being our feeling on the subject, why did we publish AIM's ad? It wasn't, you may be sure, because we particularly enjoy hitting ourselves over the head with scurrilous half-truths, means-spirited innuendos and imputations of bad faith. We published AIM's ad because it was an ad, which introduces an element that doesn't exist in the making of editorial judgments. Generally, people pay to advertise - whether it's a product or a point of view - because their message isn't something that editors would regard as worth printing as news or commentary. It is true, of course, that even ads are sometimes rejected - suppressed, if you insist - on grounds of libel, obscenity, inaccuracy or simply bad taste. But it is also true, in the case of this newspaper at least, that a certain tolerance is granted with respect to ads. And that is because we feel profoundly that the same principles that apply to the free exercise of editorial judgments also argue in favor of the widest possible freedom of expression for those who are prepared to pay to have their say.