Adventures in baby-sitting. (last word).

My little niece and nephew, I'm proud to say, have become one of the sustaining joys of my life. I've watched them from infancy through toddling to now full-fledged childhood. The oldest was born the year after I became HIV-positive, and just watching him grow and laugh and explore the world helped turn my own psychology around from thinking about death to grasping life more fully.

The more I've spent time with these kids and the more my sister insisted on bringing their gay uncle into their lives, the more I realized how great is the calumny that drives a wedge between homosexuals and children. It's the oldest blood-libel against us--that we're not to be trusted with kids, that we're all pedophiles under the skin. Of course the opposite is the case. Many gay people have children and always have--whether in same-sex or opposite-sex marriages. Gay people have always been involved in what might be thought of as surrogate parenting--in education, the arts, and the churches. There's even a theory from evolutionary psychologists that our species may have selected for a small homosexual population precisely because a group of people without offspring could help rear the children of others.

I know I'm preaching to the choir here, but I think we make too little of this point. Whether we like it or not, the association of homosexuality with a threat to children is still an alarmingly common idea. And this child-abuse libel--a trope of bigotry since it was originally applied to Jews in the Middle Ages--lies behind a great deal of the discrimination that gay people still have to endure.

Take the Boy Scouts. At one point a simple declaration that homosexuals were immoral would have kept the ban on openly gay scouts and scoutmasters in place. But now that great gay scouts and scoutmasters have been revealed, current Scout leaders have had to resort to the pedophile angle. They say barring open gays is necessary to protect kids in their charge. Never mind that closet cases stay put. Never mind that more than one adult is required to supervise kids. The "gays are child abusers" stigma fuels parental angst, which acts like a veto over reform.

Or take marriage. Here again, a chief barrier to acceptance of our inalienable constitutional right is the notion that we can't bring up kids right. This prejudice even countermands the law's usual preference for placing the custody of children with their natural mother. In a recent ruling, an Alabama judge denied custody to a natural mother because lesbianism "is an inherent evil" against which children should be protected.

This of course is a lie, and one exposed most recently by the American Academy of Pediatrics. But as a lie, it still has salience, and one of our more pressing tasks is to take it on. Many groups--PFLAG comes to mind--have helped destigmatize the interaction of gay people with children. So too do the gay families with children. But the rest of us need to do more.

We shouldn't shrink from being seen with children, or from getting involved in social work for kids, for fear of raising irrational fears. Heaven knows there are many kids--gay and straight--who need mentors, supervisors for day trips, or after-school teachers. Why not start a group that directs gay volunteers to such activities? Sure, some parents may object. But that's an opportunity for dialogue, for explaining we're not a threat--and indeed have a lot to contribute. It's also likely that many parents will welcome the idea. And the example of gay people volunteering to work with kids would be a huge message about who we really are.

Besides, it would also be good for us. Too many gay men can find ourselves oddly estranged from older and younger generations. Socializing mainly with our peer group, we tend to lose contact with kids and seniors and straight people--and our lives are poorer for it. I know what a difference my niece and nephew have made in my life. Building on that experience to reach out to other, needier kids could surely do even more. Maybe we could better ourselves by reaching out to others--and help kill a poisonous libel at the same time.

Sullivan writes for The New Republic, The New York Times Magazine, and The Wall Street Journal and writes daily commentary for www.andrewsullivan.com.