The state is acting based on political concern for the potential adopters and not for the children.

Let's stop pretending that this has anything to do with the welfare of the children. If the Catholic Church cared so much about the welfare of Children, why did they turn a blind eye pedophile priests for decades (and probably much longer), shifting them from parish to parish instead of actually dealing with their abuses of children. The Catholic Church's issue with gay and lesbian couples adopting children isn't about child welfare at all, it is simply about political agenda.