“If you redefine marriage to include same-sex couples,” he said, “you must permit adoption by same-sex couples, and there’s considerable disagreement among sociologists as to what the consequences of raising a child in a single-sex family, whether that is harmful to the child or not. Some states do not permit adoption by same-sex couples for that reason.”
The American Academy of Pediatrics opposes Scalia's view according to The New York Times.
The academy cited research finding that a child’s well-being is much more affected by the strength of relationships among family members and a family’s social and economic resources than by the sexual orientation of the parents. “There is an emerging consensus, based on extensive review of the scientific literature, that children growing up in households headed by gay men or lesbians are not disadvantaged in any significant respect relative to children of heterosexual parents,” the academy said.
Bottom line is that Justice Scalia comes off similarly to those who claim the science on climate change "isn't settled" when a vast majority of climatologists say it is. Once more, Scalia gives up any pretense of impartiality in favor of sounding like a Republican political operative.