There are difficulties in grasping this discussion from the points of view from so many. Truly, there are divisions amongst us from perspectives of each personal value system determined by our beliefs, genetic biology, exposure to lifestyles, experiences in this life, or traumatic events.
Should same gender couples be permitted by Law to adopt children? Depends,,, on an individual basis. I don't think we could blanket pass a Law that says Yes. I don't even believe that a Law should play a part in this question at all. Adoption is a very personal issue that should be determined by the intent of the ones that are taking the steps to bring a young life into their world. The conflict that comes to my mind, is about the model that is presented to the child in a same gender parent adoption. This is not my personal point of view, but one of a larger picture of the overall affect on an impressionable developing life.
The complexities of our evolution in life from a pragmatic view does not support the thought of taking your two index fingers, tip to tip, to find a point of insertion, nor does the idea of two holes manage the need as one places their thumbs upon curled fingers to create a tunnel or hole. Those that find themselves in the throws of dual satisfaction, will find ways to overcome the biology. But that does not speak to our Humanity, and the need that exists for a valued life within ourselves and the numbers of children that need an Adult to offer guidance, as they mature in life, to adulthood, regardless of the sexual proclivity, will see past the deviation of male/female biology, for the Love that can exist within the Home.
The conflict is a profundity in what might occur for the life of the child, down the road. As if we didn't have enough emotional obstacles to overcome as a species of life, now we wish to inject another form of consternation to a young mind when they see a calendar event such as Fathers Day or Mothers Day, or an event that defines Fathers and Sons or Mothers and Daughters. Exclusion/Inclusion is a part of how we grow in life, as well as is acceptance. The differences/similarities that we share with our peers, and how we handle them, are realities that we either work through, in a sense of defence or aggresion, in support of our feelings of right and wrong, or submission to what another might feel or say, determine who we are.
In my world of experience, Male partners don't wish to be parents. Though Female partners are working very hard to enable themselves to fulfill a biological function of Motherhood, and seem to be the loudest voices for this sort of Marriage and Adoption. Sounds like a valid biological response, if two females raise daughters. Men of the same gender relationships seem to be happy with themselves and only want the same marriage privilages according to the Laws that are provided. Property rights, determinations of last wish discernment's, and any sharing of that which is afforded to Heterosexual couples.