The abuse statistic, as noted above, is incorrectly portrayed by the poster. The study actually reports:
"Retrospective questions at Waves III and IV asked about adult mistreatment during childhood, including whether a parent or caregiver had “slapped, hit or kicked you,” said “things that hurt your feelings or made you feel you were not wanted or loved,” or “touched you in a sexual way, forced you to touch him or her in a sexual way, or forced you to have sex relations.” Respondents reporting any physical, verbal, or sexual abuse at either Wave were coded positive for abuse victimization. Four-fifths (79%, 95% CI 77–80) of reported mistreatment was verbal abuse." (My emphasis.)
So, only 19% of children in the study reported physical and or sexual abuse, with the other 73% being cases in which there was at least one instance of at least one of their parents saying something which "... hurt your feelings or made you feel you were not wanted or loved". What is more, from the way the question is phrased, the parent who thus abused the child need not have even been one fo the same sex couple, but may have been the partner in a prior opposite sex relationship of their natural parent.
What is more, there is something very hypocritical about this poster. The majority of opposition to marriage equality is religious based, and in Australia in particular, based on the Christian religion. It is a precept of the Christian religion that, "Those who spare the rod of discipline hate their children. Those who love their children care enough to discipline them." Paraphrasing based on the poster (and the study), "Whoever does not abuse their child, hates their child."
That, of course, is a ridiculous paraphrase, but likewise the poster is an absolute distortion in following the study in not distinguishing between actual physical abuse carefully adminstered discipline, and between actual abuse and words that merely hurt feelings. It should be noted, however, that to the extent that Christian's actually believe, and follow the teachings of their bible, one hundred percent of children of Christian parents will have experience abuse, by the standards of the poster and the study.
The study itself has face devastating criticism from Nathaniel Frank ("Comment on “Invisible Victims: Delayed Onset Depression among Adults with Same-Sex Parents”"). Frank writes:
"Sullins claims that his study examines “children raised by same-sex parents into early adulthood.” But in fact, he has zero basis to draw this conclusion, as he is applying a wholly untenable definition of “raised by.” All he knows about his dataset is that his subjects, who ranged in age from 12 to 18, spent some of their teenage years with a parent who at some point had a same-sex partner. Since we do not know if that partner was ever actually a parent, legally or otherwise, it is inaccurate to characterize such households as “same-sex parented” as Sullins does eleven times. It is even more inaccurate to claim that those living in these households were “raised by” same-sex parents, since we know nothing about the youths’ parentage before their teenage years."That criticism is a little overstated in that, "The partner parents in [Sullins'] sample were thus all designated by the children in their care as a parent, as their “mother,” “step-mother,” “father,” “step-father,” or similar." That is, they may not have been legally parents of the children, but were considered to be parents by them. But what is not overstated is that the same sex partners of the natural parents typically had not been so from birth.
Sullins defends himself on that point by saying:
"On the broadest measure of tenure, that is, time in the care of the longer-tenured parent, average parental tenure was close to current age and did not differ between same-sex and opposite-sex parent families. ... There are good grounds to say the children were “raised by” these parents."But that response is evasive. Of course the children had spent their lifetime, or nearly their entire lifetime with their 'longer-tenured parent', ie, their natural parent in the vast majority of cases. But that in no way implies they had spent a similar period with the other parent, ie, being raised by that couple. In fact, children of same sex parents had typically spent just 51% of the time living with both parents as they had with the "longest tenured parent", compared to 91% for children of opposite sex couples in the study (see Table 1). In other words, the children of same sex parents had lived about half their life (on average) without their natural parents new partner, during which period they may have had multiple other step parents, or none. They are likely to have gone through at least one traumatic separation from a prior parent.
So, in addition to inflating the abuse statistic by the very low bar ("hurt feelings"), Sullins is comparing children of stable, long term opposite sex marriage to children of same sex couples who have gone through either at least one relationship breakup, or lived most their life in a single parent household, and who are currently living with a step parent. He does not control for these extra factors. Nor does he control for the extensive bullying of the children of same sex parents that until recently was the norm, nor (come to that) the extensive persecution of their homosexual parents which used to be the norm, and which his statistics are being used to perpetuate. Like many studies aimed at attacking the LGBTI community, Sullins' study gains its results by comparing apples with oranges.