Now, how does defining marriage between one man and one woman protect children's rights and best interests? In summary,
1- Heterosexual marriage provides that a child will know and be raised by his own parents.
2- Research demonstrates conclusively that heterosexual marriage serves children's best interests.
3- Heterosexual marriage provides the child with a natural network of care and support from his immediate and extended biological family
4- Heterosexual marriage sets the foundation for the child to have the same biological, legal and care giving parents.
5- Heterosexual marriage greatly reduces the risk that children or their constituent parts will become commodities.
6- Heterosexual marriage provides children with a multi-generational sense of identity.
7- Children born from heterosexual parents have access to their own genetic heritage for medical purposes.
8- Constitutionally defining marriage between one man and one woman strengthens the judicial protection accorded to children
9-Allowing court ordered same-sex marriage to prevail creates precedent for further erosion of children's rights.
10- Heterosexual marriage protects the filiative rights of all children.
11- Defining heterosexual marriage is an absolutely essential first step in protecting children's rights and best interests.
12- Defining heterosexual marriage is insufficient to ensure adequate protection for children's rights and best interests.
13- Heterosexual marriage provides a simple and understandable set of norms.
14- Heterosexual marriage naturally protects children from potential discrimination because of the sex of their parents.
What does the ACLU have to say about this?
"Research to date has reached an unequivocal conclusion about gay parenting: the children of lesbian and gay parents grow up as successfully as the children of heterosexual parents. In fact, not a single study has found the children of lesbian or gay parents to be disadvantaged because of their parents’ sexual orientation."
How about the APA?
Like families headed by heterosexual parents, lesbian and gay parents and their children are a diverse group. Unlike heterosexual parents and their children, however, lesbian and gay parents and their children are often subject to prejudice because of their sexual orientation that can turn judges, legislators, professionals, and the public against them, sometimes resulting in negative outcomes, such as loss of physical custody, restrictions on visitation, and prohibitions against adoption. Negative attitudes about lesbian and gay parenting may be held in the population at large as well as by psychologists. As with beliefs about other socially stigmatized groups, the beliefs held generally in society about lesbians and gay men are often not based in personal experience, but are frequently culturally transmitted. The purpose of this summary of research findings on lesbian and gay parents and their children is to evaluate widespread beliefs in the light of empirical data and in this way ameliorate negative effects of unwarranted prejudice. (more at link)
Are there any outright benefits of being raised by gay parents?
Benefits. Contradicting the negative assumptions regarding lesbian parenting, a number of benefits have been documented. Four benefits accrue for children of lesbian parents (Allen 1997). First, children of homosexual parents learn respect, empathy, and acceptance of diversity. Second, some authors have argued that children of lesbian parents are also more assertive in confronting traditional sex roles and in establishing egalitarian intimate relationships. Third, children raised by homosexual parents may also learn to negotiate and maintain a healthy family in the face of legal restrictions (Savin-Williams and Esterberg 2000), understanding that families are not necessarily confined to biological events, but can be created by choice. Fourth, children in lesbian families may gain appreciation for the strengths and social support available in the gay and lesbian community (Allen 1997).
In sum, children of lesbian parents do not experience any apparent developmental disadvantage when compared to children of heterosexual parents. Overall, the quality of the child-parent relationship, not the mother's sexual orientation, is important to healthy child development.
It is valuable to look past assertion to actual data and reality.
Stacey, J., & Biblarz, T. J. (2001). (How) Does sexual orientation of parents matter? American Sociological Review, 65, 159-183.
Opponents of lesbian and gay parental rights claim that children with lesbigay parents are at higher risk for a variety of negative outcomes. Yet most research in psychology concludes that there are no differences in developmental outcomes between children raised by lesbigay parents and those raised by heterosexual parents.