I am a former anti-war activist who helped to organize the first campus demonstration against the war in Vietnam at the University of California, Berkeley in 1962. I appeal to all those young people who participated in "anti-war" demonstrations on 150 college campuses this week, to think again and not to join an "anti-war" effort against America’s coming battle with international terrorism.

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 itself. Every testimony by North Vietnamese generals in the postwar years has affirmed that they knew they could not defeat the United States on the battlefield, and that they counted on the division of our people at home to win the war for them. The Vietcong 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 Americans would give up the battle rather than pay the price necessary to win 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 anti-war activists who prolonged the struggle and gave victory to the Communists.

The second effect of the war 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 "re-education 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 anti-war movement of the 1960s.

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

I know, better than most, the importance of protecting freedom of speech and the right of citizens to dissent. But I also know better than most, 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 eventually erased. Along with thousands of other New Leftists, I was one who crossed the line between dissent and actual treason. (I have written an account of these matters in my autobiography, Radical Son). 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 Indo-China who suffered grievously from our support for the Communist enemy. I came to see how precious are the freedoms and opportunities afforded by America 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 towards 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.

This appeal is for those of you who are out there today attacking your country, full of your own self-righteousness, but who one day might also live to regret what you have done.

David Horowitz is editor-in-chief of FrontPageMagazine.com and president of the Center for the Study of Popular Culture. He also appears frequently on the Fox News Channel.

Daniel Horowitz is a contributing editor to RedState.com.  He is policy director of the Madison Project.