The idea that children just need parents who love them is like saying all they need is water to drink and they will grow up fine. Children need love as well as a moral upbringing. Putting children into homes where the morality is comprimised is wrong.
Adoption agencies should be free to follow their beliefs without being forced to place adoptions to individuals that they believe would not be best for the childs care.
If an idividual that does not meet the criteria of the religious based agencies wants the adoption, there are other agencies that do not have the same beliefs; I would suggest they use them.