When confronted with the assertion that the Soviet Union and the United States were moral equivalents, William F. Buckley responded that if one man pushes an old lady into an oncoming bus and another man pushes an old lady out of the way of a bus, we should not denounce them both as men who push old ladies around.

In other words, context matters.

Not according to some. Led by Time magazine's Andrew Sullivan, opponents of the CIA's harsh treatment of high-value terrorists have grown comfortable comparing Bush's America to, among other evils, Stalin's Russia.

The tactic hasn't worked, partly because many decent Americans understand that abuse intended to foil a murder plot is not the same as torturing political dissidents, religious minorities and other prisoners of conscience. Khalid Shaikh Mohammed was not asked to renounce his faith or sign a false confession when he was reportedly waterboarded. His suffering wasn't intended as a form of punishment. The sole aim was to stop an ongoing murder conspiracy, which is what al-Qaida is. If accounts from such unbiased sources as ABC News' Brian Ross are to be believed, his suffering saved American lives.

Comparing CIA facilities to Stalin's gulag may sound righteous, but it is a species of the same moral relativism that denounces all pushers of old ladies equally.

Consider killing. In every society in the world, murder is punished more harshly than non-lethal torture. If I waterboard you, or lock you in my basement with Duran Duran blasting at you 24/7, even if I beat you for hours with a rubber hose, my punishment will be less severe than if I murder you, simply because it is worse to take a life deliberately than to cause pain, even sadistically. We all understand this. Would you rather take some lumps in a dungeon for a month, or take a dirt nap forever?

Yet, according to the torture prohibitionists, there must be a complete ban on anything that even looks like torture, regardless of context, even though we'd never dream of a blanket ban on killing.

One reason for this disconnect is that we've thought a lot about killing and barely at all about torture. Almost no one opposes killing in all circumstances; wars sometimes need to be fought, the hopelessly suffering may require relief, we reserve the right to self-defense. Indeed, the law recognizes a host of nuances when it comes to homicide, and the place where everybody draws an unambiguous line on killing is at something we call "murder."

But there is no equivalent word for murder when it comes to torture. It's always evil. Yet that's not our universal reaction. In movies and on TV, good men force evil men to give up information via methods no nicer than what the CIA is allegedly employing. If torture is a categorical evil, shouldn't we boo Jack Bauer on Fox's "24"? There's a reason we keep hearing about the ticking time bomb scenario in the torture debate: Is abuse justified in getting a prisoner to reveal the location of a bomb that would kill many when detonated? We understand that in such a situation, Americans would expect to be protected. That's why human-rights activists have tried to declare this scenario a red herring.

Sullivan complains that calling torture "aggressive interrogation techniques" doesn't make torture any better. Fair enough. But calling aggressive interrogation techniques "torture" when they're not doesn't make such techniques any worse.

Still, there is a danger that over time we may not be able to tell the difference.

Taboos are the glue of civilization because they define what is beyond the pale in ways mere reason cannot. A nation that frets about violating the rights of murder-plotters when the bomb is ticking is unlikely to violate the rights of decent citizens when the bomb is defused. I suspect this is what motivates so many human-rights activists to exaggerate the abuses and minimize their effectiveness. Slippery-slope arguments aren't as powerful as moral bullying. Still, their fears aren't unfounded. Once taboos have been broken, a chaotic search ensues for where to draw the new line, and that line, burdened with precedent and manufactured by politics, rarely holds as firmly as the last. But that is where history has brought us.

In the recent debate over torture, everybody decided to kick the can down the road on what torture is and isn't. This argument will be forced on us again, no matter how much we try to avoid it. We'll be sorry we didn't take the debate more seriously when we had the chance.