Substantively, Ted Olson's position shows that the case for marriage equality under the law is distinct from the messier issues arising out of societal discrimination and inclusion. Of course, law can act as a lever for creating movement in society, but as the case of Roe v. Wade and abortion shows, it doesn't always resolve social and political disputes. It also exposes the utter emptiness of labels like "judicial activism" when it comes to the Supreme Court. Unless we mean to turn back the clock before Marbury v. Madison in 1804, we have to recognize that judicial review entails that sometimes the court has to fill a vacuum in constitutional jurisprudence-- i.e. "make law." The dispute is not over whether this should happen, but rather over how the court should exercise that power, and on behalf of whom.
For another take on marriage equality I highly recommend, see Martha Nussbaum's excellent article here.