When New York Gov. Eliot Spitzer was caught using a prostitution service, the irony was that he was a tough-on-prostitution politician. He took pride in locking up the same kind of people he is said to have done $80,000 worth of business with. He supported "tougher laws" to imprison customers like him.

In his statement to the news media, Spitzer called the scandal a "private matter." Good point. Adults' paying for sex ought to be a private matter, but when Spitzer was attorney general, he didn't consider paid sex private. He's one of many politicians who were eager to punish others for doing what he did.

What's going on here? Maybe these men want to punish others for acting on the same forbidden impulses they know they can't control themselves?

Rep. Mark Foley of Florida was a big advocate of punishing any adult who had sex with minors. "They're sick people; they need mental health counseling," he shouted.

But then ABC News caught Foley sending sexual instant messages to minors.

Politicians should cut back on their grandstanding, says Arizona public defender Chris Phillis, because while it's bad enough to call what consenting adults do "sex crimes," it's even worse to criminalize kids who do what kids have always done.

Phillis, who defends teens accused of sex crimes, says common sexual experimentation is now prosecuted. "If a 15-year-old touches a 13-year-old, touches their breasts, they are now guilty of a felony crime. And I would love to tell you that 13-year-olds aren't engaging in this conduct. I have a 13-year-old. But telling you that isn't going to change the fact."

The Centers for Disease Control reports that 25 percent of America's 15-year-olds say they've have had sex. Nearly 40 percent of 16-year-olds and almost half the 17-year-olds say they have. All are under Arizona's age of consent, which prompted Senate committee chairwoman Karen Johnson to try to change Arizona's sex-offender laws. She wanted to give kids a break.

But the political winds are not on her side. Few politicians want to spend political capital weakening sex-crime laws -- even when such laws have horrendous unintended consequences.

Arizona's Speaker of the House Jim Weiers defends Arizona's tough laws, saying that if you are a sex offender, "Arizona is becoming very quickly known as a state you don't want to stay in." But Weiers acknowledges that Arizona's sex-offender registry has 15,000 names on it.

I asked him how putting young people who engaged in noncoercive sex play on Arizona's registry protects the public. "I don't know if it does. ... You can't take each and every individual ... "

But it is individuals whose lives are wrecked by these laws. When Garrett Daley was 14, his 9-year-old adopted sister, Devon, said he molested her. Their mom called the police.

It turned out Devon had lied. It was she who initiated sex with Garrett. She later told the police, but they didn't believe her. Today, seven years later, prosecutors still won't let her change her testimony.

To avoid a jail sentence, Garrett plea-bargained to "attempted molestation of a child." What choice do these kids have? "They're told they'll go to jail for 90 years or 50 years or something, unless they accept this plea, and the plea almost always requires lifetime sex-offender registry," Sen. Johnson says.

Garrett didn't realize his plea bargain would put him in a different kind of jail. Once you're on the sex offender registry or on probation, your life is wrecked, public defender Phillis told "20/20."

"They can't go anywhere children frequent. So that's McDonald's, that's Jack in the Box ... Children have actually been told if you go to a movie and another child walks in, even if it's a rated R movie, then you're to get up and leave."

I told Weiers about the public defender's comments. "The public defenders say all laws go too far," Weirs replied.

Give me a break. State sex-offender registries could separate consensual teen sex from pedophiles who prey on 5-year-olds. Minnesota does that.

Too often, American criminal law is a blunt instrument designed to make it look as if politicians are protecting us. I think the politicians usually protect themselves, at our expense.