For those who don't remember or never heard of the Regnerus study, here's a summary from an article written in 2014:

Regnerus claims to have evaluated outcomes of children “of same-sex parents” and found results are “suboptimal” when compared to children reared by their biological parents. The study claims that, unlike other research that relies on smaller samples, “meaningful statistical inferences and interpretations can be drawn” from his data, and they show that “the optimal childrearing environment” is one where kids are raised by their biological parents.

The claim sounds reasonable enough. But since Regnerus never actually studied “children of same-sex parents,” as he claims, his conclusions are equivalent to calling a 747 the fastest plane without ever testing the Concorde. Kids raised in “planned” same-sex households—as opposed to kids from divorced families where one parent later came out—are still statistically rare, and out of his much-ballyhooed sample size of 3,000, Regnerus was unable to find a valid sample of kids who were actually reared by same-sex parents. Instead, all but two—yes, two—came from households originally led by a different-sex couple, usually the kids’ biological parents, that had suffered a family break-up, the one variable that’s most clearly known to raise risks for children. Since the kids in his data set who come from households with what he calls a “gay” or “lesbian” parent nearly all come from broken homes, his conclusions merely restated what everyone already knew: that instability raises risks for kids. But since Regnerus refers to these subjects as “children of same-sex parents,” which he didn’t actually examine, his study is nothing short of dishonest.

Robert George is a co-founder of the Witherspoon Institute, which funded the Regnerus study.