In writing this column, I ignore my own advice.

It’s good advice, too, given in numerous classrooms and workshops to people asking how one goes about putting an opinion piece together. Prioritize, I say. Decide which arguments are your strongest and hinge your essay on them.

I usually use my own opposition to capital punishment as an example. In my judgment, the strongest arguments against the practice are that it is irrevocable in the event of error, that it is biased by race, gender and class, and that it is expensive. But I seldom argue the death penalty on moral grounds because that can be too easily turned back on itself. I may honestly believe reverence for the sanctity of life forbids executing killers, but someone else may just as honestly believe reverence requires it. Stalemate.

Where capital punishment is concerned, morality is squishy ground.

Yet here I stand on that ground. It seems the only honest way to assay a discussion of Tuesday’s Supreme Court ruling prohibiting the execution of those who were younger than 18 when they committed their crimes. I mean, I could talk about bias, expense and irrevocability, but none of that gets close to the fundamental reason I approve the court’s action. Simply put, it was the right thing to do.

Less simply put, a civilized nation ought not be in the business of executing its children. Frankly, it ought not be in the business of executing anybody, but leave that aside for now. Because even if I considered state-sanctioned killing a proper and just response to the depravity of some criminal acts, I would still draw the line at imposing that penalty on young people.

Adolescents are, in the aggregate, less mature than their elders, less responsible, less capable of making reasoned decisions and more prone to committing foolish and impulsive acts. It’s a plain truth we have long recognized in law and custom. That’s why we protect young people from their own juvenility. It’s why we say they are too young to sign contracts, too young to drink, too young to vote, too young to see a naughty movie without parental approval.

How, then, could they have been old enough to be executed?

If we had not drawn the line on that awful practice at 18, the commonly accepted age of adulthood, where would we draw it? How young — how low — would we be willing to go? Down to Tronneal Mangum of West Palm Beach, who shot another boy to death when he was 14? Down to Nathaniel Abraham of Pontiac, Mich., who committed murder when he was 11? Or maybe, all the way down to two girls from Blythe, Calif., who, according to authorities, suffocated a 3-year-old boy when they were 5 and 6 years old.

Some, I know, would prefer we not draw a line at all. After all, drawing a line might suggest that we are, heaven forbid, not “tough on crime,” a mantra that has guided — and too often, misguided — our criminal justice decisions for more than a generation now. Between our robotic zero tolerance policies, our foolish mandatory sentencing guidelines and this zeal for subjecting children to the harshest punishments in our legal code, we have tied the system into pretzel knots seeking to prove how “tough” we are.

But as singer Gil Scott-Heron once famously noted, a cheap steak is tough, too.

Point being that toughness is not its own justification. Unleavened by compassion, logic, or just plain common sense, toughness is empty. It may gull voters and help politicians win office, may even make some of us feel all warm and righteous inside, but it does little to ensure justice.

In removing young people from death row as it did the mentally retarded three years ago, the court recognized this. It moved the country away from two especially barbarous practices and saved us from our lowest and meanest selves.

Maybe you can think of other words to describe that. For me, “moral” is the only one that fits.

— Leonard Pitts Jr., winner of the 2004 Pulitzer Prize for commentary, is a

columnist for the Miami Herald.