But now even the most conservative religious groups recognize that sex and marriage can be for non-procreative purposes. If marriages can legitimately be directed toward sexual fulfillment, then lesbians and gays also qualify. Every society ought to have laws protecting children. But heterosexual marriage as the only context for raising children has now largely become a pattern of the past. Less than half of American children live with both of their biological parents.
Adoption is permitted by single people and increasingly by same-sex couples.
Children don't need fathers as much as they need non-abusive, involved, caring parents. And, of course, gay and lesbian people can be good parents. If we are concerned about good parenting, perhaps we should train and license all adults who wish to be parents. Simply being a heterosexual couple does not magically grant the ability to raise children. Experience shows that these children of gay couples do not become gay any more often than the general population.