I guess you missed the part about extensive data available, yet this PDF Pediatric tome contains NO factual data to support its claim and is filled with hyperbolic gobbledygook.
Actually, if you had read the information and look at the referenced notes, you would have seen that it used the research contained in 17 different studies.
"20. Lamb ME. Mothers, fathers, families, and
circumstances: factors affecting children’s
adjustment. Appl Dev Sci. 2012;16(2):98–111
21. Stacey J, Biblarz TJ. How does the sexual
orientation of parents matter? Am Sociol
Rev. 2001;66(2):159–183
22. Golombok S, Badger S. Children raised in
mother-headed families from infancy: a follow-
up of children of lesbian and single
heterosexual mothers in early adulthood.
Hum Reprod. 2010;25(1):150–157
23. Bos HM, Sandfort TG, de Bruyn EH, et al
Same-sex attraction, social relationships,
psychosocial functioning, and school performance
in early adolescence. Dev Psychol.
2008;44(1):59–68
24. MacCallum F, Golombok S. Children raised
in fatherless families from infancy: a follow-
up of children of lesbian and single
heterosexual mothers at early adolescence.
J Child Psychol Psychiatry. 2004;45
(8):1407–1419
25. Vanfraussen K, Ponjaert-Kristofferson I,
Brewaeys A. What does it mean for
youngsters to grow up in a lesbian family
created by means of donor insemination? J
Reprod Infant Psychol. 2002;20(4):237–252
26. Patterson CJ. Children of lesbian and gay
parents. Curr Dir Psychol Sci. 2006;15(5):
241–244
27. Wainright L, Russell ST, Patterson CJ. Psychosocial
adjustment, school outcomes,
and romantic relationships of adolescents
with same sex parents. Child Dev. 2004;75
(6):1886–1898
28. Tasker F. Lesbian mothers, gay fathers, and
their children: a review. J Dev Behav
Pediatr. 2005; 26(3):224–240
29. Perrin EC. Sexual Orientation in Child and
Adolescent Health Care. New York, NY:
Wolters Kluwer; 2002
30. Patterson CJ. Children of lesbian and gay
parents. Child Dev. 1992;63(5):1025–1042
31. Anderssen N, Amlie C, Ytterøy EA. Outcomes
for children with lesbian and gay parents. A
review of the studies from 1978 to 2000.
Scand J Psychol. 2002;43(4):335–351
32. Goldberg AE. Lesbian and Gay Parents and
Their Children: Research on the Family Life
Cycle. Washington, DC: American Psychological
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33. Perrin EC; American Academy of Pediatrics,
Committee on Psychosocial Aspects of
Child and Family Health. Technical report:
coparent or second-parent adoption by
same-sex parents. Pediatrics. 2002;109(2):
341–344
34. Pawelski JG, Perrin EC, Foy JM, et al The
effects of marriage, civil union, and domestic
partnership laws on the health and
well-being of children. Pediatrics. 2006;118
(1):349–364
35. Wainwright JL, Patterson CJ. Delinquency,
victimization, and substance abuse among
adolescents with female same-sex parents.
J Family Psychol. 2006;20(3):526–530
36. Wainwright JL, Patterson CJ. Peer relations
among adolescents with female same-sex
parents. Dev Psychol. 2008;44(1):117–126
37. Golombok S, Perry B, Burston A, et al
Children with lesbian parents: a community
study. Dev Psychol. 2003;39(1):20–33"
And the combined information from those 17 studies was used as the basis for the pediatric recommendations.
And the study done by Melbourne University in Australia (I linked it previously) shows good research numbers.
"The Australian Study of Child Health in Same-Sex Families, called the world's largest study of its kind, drew upon health data from over 500 children aged 5-17 and 315 gay, lesbian and bisexual parents"
As for the study presented by the FRC, there are quite a few flaws in the research methods used.
"While Regnerus critiques "same-sex couples" raising kids, his study does not actually compare children raised by same-sex couples with those raised by different-sex couples. The criterion it uses is whether a parent "ever ha[d] a romantic relationship with someone of the same sex." In fact, only a small proportion of its sample spent more than a few years living in a household headed by a same-sex couple. Indeed, the study acknowledges that what it's really comparing with heterosexual families is not families headed by a same-sex couple but households in which parents broke up. "A failed heterosexual union," Regnerus writes in the study, "is clearly the modal method" — the most common characteristic for the group that he lumps in with same-sex-headed households. For example, most of the respondents who said their mothers had a lesbian relationship also endured the searing experience of having their mothers leave the household as the family collapsed."
"Regnerus seeks to enhance the credibility and relevance of this body of research by including in his sample respondents who actually had a gay parent instead of just people from broken or single-parent homes. But because his sample is mostly made up of fractured families, he fails the most basic requirement of social science research — assessing causation by holding all other variables constant. What he has produced is no better than its predecessors at yielding insight into the effect of same-sex parenting. [LA Times, 6/13/12]"
"Gary J. Gates, author of The Gay and Lesbian Atlas and Williams Distinguished Scholar at UCLA Law School, criticized Regnerus's comparison between children of intact heterosexual families and children whose parents had at some point had a same-sex relationship — the latter group, he noted, had experienced divorce, step-parent arrangements, and foster care, all of which are known to affect children's lives no matter what the sexual orientation of their parents.
"The methodology," he said, "is designed to find bad outcomes" for children with same-sex parents.
Regnerus argues that he simply couldn't find enough intact same-sex-parented families to do a comparison, but Gates counters that "if you have limited sample size then you can't do the analysis."
Gates called the findings obvious: "All he's shown us is that family instability isn't good for kids. [BuzzFeed, 6/12/12]"
So the FRC study compared intact heterosexual families with broken families in which one of the parents was involved in a same-sex relationship at some point. Yeah, that is great research. Great research if you know what point you want to prove and don't mind working directly towards it.