Subject to interpretation and conjecture? That children being born outside of a committed union is a bad detrimental to the children, and as a result, society overall? Curiously you don't state where this 'interpretation" comes into play.
We have entire cultures that can be compared in the same societies where the outcome of the offspring and the culture, is consistently recognized to be problematic when marriage is not held in esteem, but prositive for those cultures overall and in their advancement in society.
One cannot look at the 5-4 decision and fail to recognize it is along ideological lines. To eviscerate Kennedy's majority opinion indicated as, " the right to liberty and to equal protection for gay couples", the equal protection clause of the 14th Amendment only deals with opportunity, not outcome, and certainly not any guarantee of recognition and reward by society, and not under different terms, which is the social engineering being promoted by the court's majority.
As far as Prop 8, it is hard to fathom that this country, and Court. might believe that a people do not have the authority to affirm their terms of society, and instead the government can dictate those terms to the people, which is precisely what is expressed by Kennedy:
The essence of democracy is that the right to make law rests in the people and flows to the government, not the other way around. Freedom resides first in the people without need of a grant from government. The California initiative process embodies these principles and has done so for over a century.
The actions of the court, and the government, have grossly undermined that freedom.