AS a former antiwar activist who helped to organize the first campus demonstration against the war in Vietnam at UC Berkeley in 1962, I appeal to all those young people who are participating in antiwar demonstrations on college campuses now to reconsider.

The hindsight of history has shown that our efforts in the 1960s to end the war in Vietnam had two practical effects.

The first was to prolong the war. Since the war ended in 1975, North Vietnamese generals have said that they knew they could not defeat the U.S. on the battlefield, so they counted on the division of our people at home to win the war for them. The Viet Cong forces we were fighting in South Vietnam were destroyed in 1968. In other words, most of the war and most of the casualties in the war occurred because the dictatorship of North Vietnam counted on the fact that Americans would give up the battle rather than pay the price necessary to finish it. This is what happened. The blood of hundreds of thousands of Vietnamese and tens of thousands of Americans is on the hands of the antiwar activists who prolonged the struggle and gave victory to the communists.

The second effect springs from the prolonging of the war, and that was to surrender South Vietnam to the forces of communism. This resulted in the imposition of a monstrous police state, the murder of hundreds of thousands of innocent South Vietnamese, the incarceration in reeducation camps of hundreds of thousands more and a quarter of a century of abject poverty imposed by crackpot Marxist economic plans, which continue to this day. This, too, is the responsibility of the so-called antiwar movement of the 1960s.

I say "so-called" because while many Americans were sincerely troubled by the U.S. war effort, the organizers of this movement were Marxists and radicals who supported a communist victory. Today, the same people and their followers are organizing campus demonstrations against America's effort to defend its citizens against the forces of international terrorism and anti-American hatred responsible for the Sept. 11 attacks.

I know better than most the importance of protecting freedom of speech and the right of citizens to dissent. But I also know that there is a difference between honest dissent and malevolent hate, between criticism of national policy and sabotage of the nation's defenses. In the 1960s and 1970s, the tolerance of anti-American hatreds was so high that the line between dissent and treason was erased.

Along with thousands of other New Leftists, I was one who crossed the line between dissent and actual treason by publishing classified government information in Ramparts magazine. I did so for what I thought were the noblest of reasons, to advance the cause of social justice and peace. I have lived to see how wrong I was and how much damage we did--especially to those whose cause we claimed to embrace, the peasants of Indochina who suffered grievously from our support for the communist enemy. I came to see how precious are the freedoms and opportunities afforded by the U.S. to the poorest and most humble of its citizens and how rare its virtues are in the world at large.

If I have one regret from my radical years, it is that this country was too tolerant toward the treason of its enemies within. If patriotic Americans had been more vigilant in the defense of their country, if they had called things by their right names, if they had confronted us with the seriousness of our attacks, they might have caught the attention of those of us who were well-meaning but utterly misguided. And they might have stopped us in our tracks. I appeal to those of you who are attacking your country, full of self-righteousness, who, like me, may live to regret what you have done.