If Republican presidential candidates want to debate sexual health and hygiene, it would be nice if they displayed more collective knowledge and judgment than your average eighth-grade family life class. During the Tampa debate, one longed for a blunt, part-time football coach -- or whomever they draft into teaching health classes nowadays -- to mount the stage and present the facts of life.

The human papillomavirus (HPV) is a nasty sexually transmitted disease contracted by about three-quarters of Americans at some point. You can have it, and spread it, without knowing it. In some women, the virus causes abnormal cells in the lining of the cervix that can develop into cancerous lesions. Virtually all cervical cancer is caused by HPV.

There is, however, a vaccine that is highly effective against the most dangerous HPV strains. Its main side effect -- as you'd expect when sticking a needle into a preteen girl -- is fainting. The Centers for Disease Control and Prevention recommends that all girls should get it anyway.

At least this approach would have added to the public stock of health information. Instead, Michele Bachmann talked of "innocent little 12-year-old girls" who were "forced to have a government injection" by Rick Perry's 2007 mandate of HPV vaccinations in Texas.

Bachmann later added, on the medical authority of a weeping anecdote, that the HPV vaccine, or maybe it was some other vaccine, might cause "mental retardation." Bachmann herself seems prone to a serious condition: the compulsive desire to confirm every evangelical stereotype of censorious ignorance.

The objections to routine HPV vaccination cluster in a few areas. First, it is alleged that removing medical penalties for sexual contact -- in this case, HPV and cervical cancer -- will encourage sex. A protective shot given to a girl on the verge of sexual maturity, in this view, may be taken as permission for experimentation.

This type of argument is inherently difficult to prove or disprove. But it is unlikely that a 16-year-old making sexual choices is focused on her chances of getting a cancer that might develop 20 years in the future -- a hypothetical event beyond the time horizon of the adolescent mind.

The more disturbing moral failure concerns any parent who would entertain this argument.

Try to imagine a parent-daughter conversation about sexual restraint and maturity that includes the words: "Honey, I'm going to deny you a vaccine that prevents a horrible, bleeding cancer, just as a little reminder of the religious values I've been trying to teach you."

This would be morally monstrous. Such ethical electroshock therapy has nothing to do with cultivation of character in children. It certainly has nothing to do with Christianity, which teaches that moral rules are created for the benefit of the individual, not to punish them with preventable death.

This approach to moral education may appeal to a certain kind of conservative politician. How could it possibly appeal to a parent, conservative or otherwise?

A second objection to routine HPV vaccination concerns parental rights. Bachmann confused this issue by introducing antivaccine paranoia -- one of the most direct and practical ways that a public official can undermine the health of his or her fellow citizens.

A more sophisticated version of this argument claims that a vaccine against measles or mumps is fundamentally different from a vaccine against a sexually transmitted disease such as HPV. Because of the ethical context, parents should have more of a say.

But the public health case for vaccination is similar for diseases spread by coughing or diseases spread by sexual contact. Vaccines decrease the incidence of a disease in a whole society, which has good health outcomes for everyone, not only for the protected individual.

Consider a woman who is resolutely abstinent until her marriage at 24. Her husband -- who got HPV from a girlfriend who was not vaccinated -- unknowingly gives it to his wife on their wedding night, increasing her risk for cervical cancer. She would suffer because others are not vaccinated.

The decision to vaccinate -- for HPV or any infectious disease -- is not just a personal, family choice. It is also a matter of public health. And it is not unreasonable for public authorities to strongly encourage responsible parental choices.

It is possible that Rick Perry encouraged HPV vaccinations in the wrong way or for the wrong reasons. But it is Bachmann, not Perry, who would put girls and women at risk based on moral confusion and public health illiteracy.

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Michael Gerson's column is distributed by the Washington Post Writers Group.