Psychologist: I'm gonna study how the kids of lesbians turn out. Hey lesbians, how are your kids?
Lesbian moms: They're pretty good
Psychologist: Nice
This is hardly the only study to do this, if you look at the APA's 2005 brief on homosexual parenting(mentioned in your article) many of the studies rely simply on the reporting of the parent to measure the outcome in addition to several other reoccurring problems with that research like small samples sizes, unrepresentative samples, and in some cases even a lack of a control. As a guy who graduated with a degree in psychology I'm going to cosign
@Zankou's claim that psychologists are terrible scientists. The APA has shown itself willing to take politically convenient but scientifically weak positions.