Anything and everything can be equivocated.
OK, give me some concrete examples where a child raised in a household with two parents of the same sex/gender acted in a manner that caused grave damage to some segment of society?
I'm saying that I don't think such conclusive proof exists. If you think it does, let me know what fits that category for you.
There are plenty of studies to choose from that indicate that a child is better off in many ways having a mother and a father in the household. The fact that the parents in a household love each other is only part of the equation. (Marriage and the Family by the American College of Pediatricians available at
https://www.acpeds.org.) (Marriage and the Family by Child Trends available at
https://www.childtrends.org.) (Family Matters: Family Structure and Child Outcomes by the Alabama Policy Institute available at
https://www.alabamapolicy.org.)
Having a father in the home reduces behavioral problems in boys and psychological problems in girls, enhance cognitive development, and decrease delinquency. (Sarkadi, A., Kristiansson, R., Oberklaid, F., & Bremberg, S. (2008). Fathers’ involvement and children’s developmental outcomes: A systematic review of longitudinal studies. Acta Paediatrica, 97, 153-158.)
It is also known even by pro same sex marriage people that there are few longitudinal studies on children raised by lesbians and none on children raised by homosexual men. I am assuming findings of many studies of this sort is what you are looking for in relation to "concrete evidence". There is not enough of that type of evidence to confirm one way or another if that is the sort of validation you are seeking.
If countless research has gone into and come to the conclusion that children are best off with both a father and and a mother in the home, anything else would have a negative impact from what could be.
I've said this before, and I will say it again, while I don't support it, in some cases it is better than some of the other realities we have out there. Two good parents whether heterosexual, or homosexual can be better than having an abusive parent in the home, or depending on the situation only one parent in the home. There are a lot of factors that are involved in a home and raising a child. That being said, I will continue to support and defend what I see as the best scenario for children, families, my community, and nation. Feel free to see things differently, but I will continue to voice my opinion.
I don't have time to get more into this at the moment, this will have to do as a start.