ON TELEVISION, the brother of one of the kids killed by John Wayne Gacy stood outside the courtroom and said he was glad that gacy had been sentenced to death for his crimes. He was a very outspoken young man, very frank about what he felt. Gacy's death would not bring back his brother, he said, but it was revenge and revenge, as we all know, is sweet.Amen.

He was right. Somewhere in me, the other shoe dropped. Here was a case in which an eye was going to be taken for an eye. There is something about that that is nice and neat, that leaves no strings untied. No loose ends. How perfect. The television set went to a commercial and my wife turned and asked me how, as an opponent of capital punishment, I felt.

I felt fine, I said. I did not care about Gacy. He killed 33 boys, after all. He was a monster if ever there was one and if anyone should be executed he should be. Hang him. Burn him. Shoot him. What do I care? Just get rid of him.

But then my memory quickly flashed to something else I had recently seen on television. It was a reporter on the Polk Awards for distinguished journalism. I paid a lot of attention because a friend of mine had won an award, but I did not see my friend. I saw something else. I saw that two prisoners from the state penitentiary at Angola, La., had also won Polk Awards. They were both killers.

The camera took us into the prison where the two men were shown sitting at their typewriters, working on yet another edition of the penitentiary newspaper, the Angolite. One of them had written an article about homosexuality in prison -- an article about brutality and rape and subjugation. The other had written about possible misfeasance in the murder of a prisoner. Both men are serving life terms. Both men might have been condemned to death and the death penalty been constitutional back when they were convicted.

In a nutshell, this is what the problem is with the death penalty. It is not much of a problem when you are talking about Gacy or some other person who kills persistently and over a long period of time, but you cannot write a law just for the likes of him. The law has to be fair and equitable. It has to say, in a very constitutional way, that the state can take your life for murder -- certain types of murder, anyway. You can't exempt a person because you like the way he looks or because he's only killed once, or because you believe, for some reason you can't put your finger on, that he's worth saving.

There is, of course, a further problem. Just recently, Dr. Herman Tarnover, the creator of the Scarsdale Diet, was shot and killed. His alleged assailant is the headmistress of a very swanky school in Virginia and she makes what used to be called a nice appearance. Under no circumstances is it conceivable that someone like her could be executed. She is so well estimated. She looks too sweet.

The fact of the matter is that in a nation that is largely white and middle class, the people who get executed largely are not white and not middleclass. They are usually poor and black and they are especially likely to be executed if the person they have killed is not one of their own, but, say, white and middle class. This, many people think, is the truly unforgivable murder.

So Gacy is not the issue and the issue is not whether he's worth saving or not worth saving. The issue is capital punishment itself, which seems woven in the American social fabric. We almost alone among nations want it. We must have it and yet it does nothing. It is no deterrent and it does not bring back the dead and it can never be fairly administered and it is always irrevocable. Make a mistake here and it's too late to say you're sorry.

So sometimes in the very distant future, after lot appeals and hearings and delays. John Wayne Gacy may be executed. If that happens, almost nothing else will happen. The boys he killed will not come back and no other murderers will be deterred and parents will feel no more comfortable when their children are missing in the neighborhood -- even the very same neighborhood where Gacy lived. Only one thing will happen: The brother who said he wanted revenge will get it.

I understand his reason. What's ours?