The revived debate over American policy in El Salvador is floundering again on the same political fallacies which prevented any reasonable public discussion of the Vietnam war.
The primary myth is that communists are revolutionaries, as noncommunists define revolution; that is, idealists seeking to fulfill the total aspirations of the masses. A second fallacy is that a revolutionary movement can be staged in any strategic part of the world without communist involvement. A third decrees that the United States has neither the necessity nor the right to become involved in a ''local revolution.''
These concepts were refuted long ago by events, but they persist. They have been kept alive both by supportive propaganda and the tendency of many Americans to reject any indictment against the communists because of the sometimes exaggerated charges made against them. Finally, another political fallacy is involved: If one side is wrong, or appears wrong, in a political controversy, the other side automatically is right.
The reality of today's complex world is that both sides are wrong in such upheavals as El Salvador, Nicaragua, Vietnam, and many others. Realistically, the challenge for American policymakers -- and for true humanists -- is to support the side which appears to be less wrong or less permanently wrong.
On paper, a revolution controlled by communists corresponds to the traditional dictionary definition: ''overthrow of a government or form of government or social system, with another taking its place.'' But this definition is inadequate for today's world. The real issue is whether the revolutionary leaders intend to fulfill their promises or are running a deliberate political con game.
Communist leaders have proved repeatedly, most recently in Poland, that they will not tolerate fulfillment of the primary aspirations raised by all social revolutions, particularly their own. They will allow no individual freedoms but instead maintain the most thorough dictatorship in history. They will not permit independent labor unions and have no intention of giving ''land to the tillers, '' or granting their other promised social improvements, with the notable exception of propagandized education. What they do give is relative equality to the downtrodden and bread to the starving, in exchange for political servitude. This is not enough, as the revolts in nearly every communist country and the escape of millions have demonstrated.
Even Vladimir Lenin, founder of the Soviet Union, recognized that the ordinary man would not knowingly fight and die for the actual communist system, so he created techniques to lure him into supporting the system before he knows what it is. Communist leaders, for example, talk more about human rights than anyone else, while suppressing them more ruthlessly than the most dictatorial noncommunist leadership. Lenin, whose tactics are used today by all parties, also devised propaganda appeals and manipulative techniques to win support from the world's liberals -- whom he despised and whom he promised to eliminate first after communist victory in any country.
One Leninist tactic is particularly influential in Central America. Communist leadership of any revolutionary movement is deeply disguised, primarily for subterfuge. The communists, for example, hijacked a successful noncommunist revolution in Russia; they led an ''agrarian reform'' movement in China, a ''workers' party'' in Vietnam, and Castroite ''liberalism'' in Cuba. In each instance, the true nature of the new regime was revealed only months or years after victory.
Nicaraguan and now Salvadoran rebels clearly are following the same pattern. They pose and are widely accepted as simply revolutionaries fighting admittedly repressive regimes. Even if this were true, history has shown that not all noncommunist leaders have been able to fight off the domination of communists whose help was accepted to win a social revolution. There is no precedent to show that men who quote Marxism-Leninism, accept substantial communist arms shipments, adopt ''reforms'' from the exact blueprints used in communist countries, and collaborate with communist powers involved in a neighboring insurrection will turn out to be democrats.
The probability that, with victory, the Salvadoran rebels would join Nicaragua to further Soviet-Cuban efforts to capture all of Central America and to use this position for constant pressure on the US not only justifies but demands full Washington support for the Salvadoran government. So do humanitarian considerations. The political issue is whether the country will fall under inflexible dictatorship or will seek more of the reforms which already have begun, however tentatively.
Russell Brines, a free-lance writer, has covered foreign affairs and particularly communist affairs for 40 years as a journalist and author.