Have you ever pondered the irony that many if not most of those who argue most vociferously against adoption by gay couples are themselves - because of their prejudice - far less suitable to adopt a child?
"But, but", you may say, trying to be objective, "Surely, nearly everyone has some prejudices and if we were only to allow those who were totally free of prejudice to adopt, there'd be very few adoptions".
However, in this context, anti-gayness is subtly different from other forms of bigotry. A couple who don't like people of African origin won't adopt a black child. An anti-Chinese couple will steer clear of children from that ethnic background.
When a couple adopts a child, no-one knows what orientation that child will have. He/she may turn out to be gay and if the parents hate gay people, then that child will have been delivered into an environment which will in time turn out to be very emotionally damaging for them.
Is this something adoption agencies consider when allowing people to adopt children? I hope so but when you think of all the third world adoptions going on, you would wonder. I doubt that authorities in the Philippines or Vietnam care much about it.