Regnerus has conducted research on the impact of a child having a parent who has been involved in a same-sex relationship. A 2012 population-based study of his in Social Science Research[9] generated protracted debate and controversy.[10][11] This included a disavowal by Regnerus' department chair at the University of Texas-Austin, in which Christine L. Williams cites the American Sociological Association, "which takes the position that the conclusions he draws from his study of gay parenting are fundamentally flawed on conceptual and methodological grounds and that findings from Dr. Regnerus’ work have been cited inappropriately in efforts to diminish the civil rights and legitimacy of LBGTQ partners and their families."[12] Two hundred social scientists, led by Gary Gates, signed the "Letter to the editors and advisory editors of Social Science Research",[13] in which they express their concern "about the academic integrity of the peer review process for this paper as well as its intellectual merit."[14] Regnerus continues to defend the research.[15][16]
The controversy also resulted in an audit of the review process used by Social Science Research.[17] Critics have largely focused their attention on the few same-sex relationships in the data, faulting Regnerus for comparing the adult children of intact (heterosexual) families with those whose parents may have purportedly formed same sex relationships after the dissolution of a heterosexual union.[18][19] In June 2012, 27 scholars signed a response to the Regnerus Controversy in defense of Regnerus' research, stating: "we think much of the public and academic response to Regnerus is misguided for three reasons."[20] They also argue that "it is possible to interpret Regnerus’s findings as evidence for the need for legalized gay marriage, in order to support the social stability of such relationships," which contrasts with Regnerus' own conclusion published in Slate: "[this study] may suggest that the household instability that the NFSS reveals is just too common among same-sex couples to take the social gamble of spending significant political and economic capital to esteem and support this new (but tiny) family form".[21] Major academic organizations including the American Sociological Association, American Academy of Pediatrics and American Medical Association dispute the validity of Regnerus' data and conclusions reached thereof, arguing that unlike previous studies, the statistically tiny number of same sex couples in a study whose sample group largely consisted of failed heterosexual marriages where one of the parents was allegedly homosexual, make it impossible to extrapolate any information about same sex parenting. A review carried out by the American Medical Association noted that:[18]
... The data does not show whether the perceived romantic relationship ever in fact occurred; nor whether the parent self-identified as gay or lesbian; nor whether the same sex relationship was continuous, episodic, or one-time only; nor whether the individual in these categories was actually raised by a homosexual parent (children of gay fathers are often raised by their heterosexual mothers following divorce), much less a parent in a long-term relationship with a same-sex partner. Indeed, most of the participants in these groups spent very little, if any, time being raised by a “same-sex couple.”[18]
Some argue that the project's funding source, the Witherspoon Institute, a conservative think tank, ultimately biased the results;[22][23] New York Times writer Mark Oppenheimer speculated that Regnerus' Catholic faith may have shaped the way he approached the study of same-sex relationships.[10] When asked whether his funding source (the Witherspoon Institute) is conservative, Regnerus responded by stating, "Yes. And the Ford Foundation is a pretty liberal one. Every academic study is paid for by someone. I’ve seen excellent studies funded by all sorts of interest groups."[24]
Regnerus contributed to an amicus brief in opposition to same-sex marriage[25] and appeared as an expert witness in a 2014 federal court hearing regarding Michigan's ban on same-sex marriage. Citing widespread criticism of NFSS methodology, Judge Bernard A. Friedman rejected Regnerus' testimony, alleging the arguments derived from methodologically flawed data were "not worthy of serious consideration" and served rather to please the conservative organizations (Witherspoon Institute and Bradley Foundation) that underwrote the survey research project.[26]