THE season of witch hunting in the Soviet Union has already begun despite warnings from Vadim Bakatin, the new head of the KGB. I talked with him on the day he was appointed to take over for former KGB chief Vladimir Kryuchkov, who is under house arrest for his role in organizing the coup. "This would be the most terrible thing to happen, if, after defeating one form of lawlessness - one form of a totally idiotic adventurist conspiracy - we were to make a U-turn and start a witch hunt, revengeful acts, self-trials, searches for archives," Mr. Bakatin said. But that is exactly what has begun. The most prominent member of the newly depicted coven of witches includes the members of the Emergency Committee. These architects of the coup are under house arrest, awaiting word of their fate. There is talk of a criminal investigation or even the death penalty for treason against the state. They stand to be punished most severely since they are, after all, the first coven. The second coven of witches includes those officials who failed to stand up against the Emergency Committee and thereby committed crimes of omission rather than commission. The new code word for this offense in the Soviet Union is "passivity." The irony is that the Soviet people have been forced into passivity by a system which, until recently, created little incentive to challenge the prevailing view. One of the first to be branded with the new crime of passivity was Soviet Foreign Minister Alexander Bessmertnykh. He was sentenced by Mikhail Gorbachev in a terse phone call last Friday in which the president asked for Mr. Bessmertnykh's resignation. The stunned foreign minister never had a chance to defend himself, except in the media. He tried to argue, in an interview with Ted Koppel, that his actions or inactions were done to protect Soviet foreign policy. Whatever one may think of his explanations, Bessmertnykh's warning merits attention: "I think we shall have maybe a little of that leftist McCarthyism because of the enthusiasm of the people who were on the barricades. And now they ask everyone, 'Where were you during those three days? Were you on the barricades? And if you were not on the barricades, aha, that is something suspicious. Who are you?' " The McCarthyism which Bessmertnykh refers to is most likely to emerge as the witch hunt grows to include people whose only crime was being loyal members of the Communist Party. Mr. Gorbachev warned Boris Yeltsin at last week's Russian Parliament session against branding all Communists as traitors. Millions of Soviets devoted their lives to the party out of fear or coercion; others because there was little else to believe in. The failure to distinguish between coup collaborators and ordinary rank and file Communists creates the potential for violent anti-Communist crusades. The final coven includes those who will be found guilty by association. Mr. Yeltsin's blanket order to close down Pravda, the Communist Party daily, and Izvestia, the Soviet government daily, presumes that all those who worked for these institutions supported the coup plotters. What about those journalists who chose to stay home in passive protest? The only way to sort out which side of the barricade one was on is to individually question everybody. Are we to see in the Soviet Congress of People's Deputies a Committee on Un-Soviet Activities? Are we to see blacklisting and red baiting reminiscent of the 1950s in America? Soviet history is replete with examples of power shifts, putsches, and counter-putsches. After every revolutionary spasm has come a period of revenge and house cleaning. The challenge the Soviet Union faces today is how to clean house without tearing down the basic structures on which a true democracy might be built. It's the challenge implicit in the Renaissance epigram, "The noblest vengeance is to forgive."