I would never dispute that two men or two women could do a good job at many parenting tasks--- in the sense of being able to feed, clothe, shelter and educate a child, be warm and responsive, shield him from danger, and foster his God-given gifts. These competencies may be found in SS couples as in mom & dad couples... as well as in orphanages, group homes, mother-grandmother households, or any number of permutations and combinations of caregivers.
Clarence Thomas was raised by his grandfather: so even a single-parent home can produce well-raised kids.
But the very fact that the child is set up for a planned adoption or conception via artificial insemination or IVF or surrogacy --- by two men or two women, means they think that there is nothing particularly desirable about natural fatherhood and motherhood and/or that a child has no right to his mother or father. THEY WANT IT THAT WAY. THEY PLAN IT THAT WAY.
They're deficient in the very area where diversity and balance counts: diversity in relating to a father AND a mother, and balance in experiencing day by day the affective complementarity of marriage: of a man and a woman in a good marital relationship.
Novelist Walker Percy and his two younger brothers were raised well by their homosexual but singleton second cousin, William Alexander Percy, when their parents both (apparently) committed suicide. God protect those who are thrust by happenstance into a broken situation. Bless the caregivers, imperfect as they may be, who do as well as they can. Sometimes --- often --- a child could get stuck in a an unbalanced situation by tragedy or chance.
But it should not be imposed on any child by choice.
Very well said.