...is not determined by the State.
Do those who favor adoption by homosexual couples really think that the Catholic Church does not have the best interests of the children in mind?
Are there not adoption agencies that DO allow adoption by homosexual couples? If so, leave the Catholic Church alone to do what it thinks best for those children entrusted to its care by the parents.
If there is NOT such an adoption agency, then go start one. Call it GLBT Adoption Agency, and see how many parents place their children there.