Adoption doesnt change that fact that only heterosexuality has biological and evolutionary components.
As has been explained to you often, this is also flatly false. Your refusal to acknowledge it is false does not change that it is false.
So you agree with me. Gay marriage proponents need to justify the changes in society that they are requesting.
At what point did I say "changes in society" need to be justified? I said treating people differently needs to be justified.