A quote from the majority decision written by Chief Justice Ron George:
Our state now recognizes that an individual's capacity to establish a loving and long-term committed relationship with another person and responsibly to care for and raise children does not depend upon the individual's sexual orientation...What this means, in effect, is that the state of California now recognizes error as truth and the law of the land.
To begin with, one's ability "to establish a loving and long-term committed relationship with another person" is indeed dependent upon "sexual orientation," if by "a loving and long-term committed relationship with another person" one means a relationship with a sexual aspect. This is because to love someone is to will their good for their own sake. If you are willing to enter into some type of sexual congress with a member of the same sex, then you also will that they enter into sexual congress with you. But such an act is contrary to the nature of the sexual act, since the sexual act is by nature ordered towards procreation and sexual acts between two persons of the same sex are, in their essence, not ordered towards procreation. Thus these sexual acts are evil. And following from that, if you will another to enter into such an act with you, then you are willing them evil. Thus, insofar as you are willing to enter into some warped form of sexual congress with another member of the same sex, you are not loving them. This is necessarily true.
Second, one's ability "to care for and raise children" is also dependent on "sexual orientation," at least insofar as we are talking about the people caring for and raising children being in a sexual relationship with one another. This is because the caring for and raising of children includes not only their material needs, but also their moral and spiritual needs. The very existence of a same-sex sexual relationship between those in charge of the caring for and raising of children presents a moral and spiritual danger to said children. This is because such a relationship teaches children that acts and inclinations that are objectively disordered are instead rightly ordered. The very existence of a same-sex sexual relationship between those charged with the raising of children is a moral and spiritual poison that will lead the children to believe that a lie is the truth and that an evil is a good. Which, I suppose, is par for the course in the modern world.