Spanking was a subject of debate on every parenting website on the continent during the past week, and I don't understand why.

Yes, I know why it was a topic of conversation -- the prestigious journal Pediatrics released a study early in the week showing a possible link between childhood spanking and mental health struggles later in that child's life, and that was news worth talking about.

What I don't understand is why it was a debate. By definition, that would require two sides. I see only one.

At what point does something become simple fact? The Pediatrics article was just the latest in a decades-long march of studies showing spanking -- defined as hitting with an open hand in order to correct or punish -- to be ineffective at best and psychologically harmful at worst.

In April, an article in the Canadian Medical Association Journal analyzed two decades of data and concluded that spanking has no upside, and its downsides include increased risk for depression, anxiety, substance abuse and aggressive behavior later in life.

A few years earlier, another Pediatrics study, this one by researchers at Tulane University, concluded that children who are spanked as often as twice a month at age 3 are twice as likely to become aggressive, destructive and mean when they are 5.

And it has been a decade since Columbia University psychologists went through more than 80 studies over 62 years and found that there was a "strong correlation" between parents who used "corporal punishment" and children who demonstrated 11 measurable childhood behaviors. Ten of the behaviors were negative, including such things as increased aggression and increased antisocial behavior. Only one could be considered positive -- spanking did result in "immediate compliance."

So would pointing a gun in their general direction. But that does not make it the right thing to do. And, as other research points out, if that temporary compliance comes at the price of long-term depression or defiance, then what has really been gained?

In spite of this mountain of data, though, polls and studies find that up to 90 percent of parents spank their children. And each time we parenting reporters write about the latest studies, our comment threads fill with practitioners, whose remarks range from outrage ("I was hit and I turned out okay god damn it") to despair ("I don't want to hit, but it is the only way I can get them to listen"). (You can get the idea here...)

I am continually amazed at what it takes to redirect parenting opinion. It is dizzying how quickly one study or article can -- sometimes -- change our ways. We started placing infants on their backs rather than their stomachs when there were hints of correlation, but not proof of causation, with crib death. Pregnant women stopped having sushi, soft cheese, caffeine and even a sip of alcohol on the remote but striking possibility that a small amount could have consequences. BPA bottles disappeared in certain circles overnight when there was an unofficial link to cancer.

But other times, we just don't want to know. In that way the spanking conversation is like the vaccine "debate." In spite of no credible evidence of a link with autism, and many studies that tried and failed to find such a link, there are some minds that just won't change.

Your parents hit you, and you are okay? They probably smoked around you, too, and they didn't make you wear a seatbelt, either, but we know better now. Also, might I respectfully ask how you know that you're okay? Perhaps if your parents hadn't hit their kids, you wouldn't feel a need to hit your own?

It is the only thing that works when your children won't listen? Swedish children are not running amok in the streets, and spanking has been illegal there since 1979. Sweden was the first of 32 countries -- including Costa Rica, Israel, Kenya and most of Europe -- to approve such a law.

Some questions really don't have two sides. "Is it okay to do something to your child that would land you in jail if you did it to a stranger on the street?" is one of those. You can phrase it other ways too -- like "Is it okay to hurt a child because it serves your immediate goal when science shows it can lead to long-term harm?" But there is still just one answer.

And yet, we keep seeing it presented as a disagreement.

"To Spank or Not to Spank" was the headline on both the CNN's report yesterday and the "Good Morning America" segment on Thursday about the latest Pediatrics study. The "Today" piece added the tagline: "Mommy Wars: Raging Parenting Debate," and a Babble blogger was found to represent each side.

But there aren't two sides. There is a preponderance of fact, and there are people who find it inconvenient to accept those facts.

Where, exactly is the debate?