The traditional Jewish community does not marry a male member of the priestly lineage with a divorcee or a convert, nor can a child of an adulterous union marry any Jew at all. Despite the fact that civil marriage is offered to each of these couples, one hears no protest from the Orthodox community over the violation of its sensibilities. Orthodox communities have grown accustomed to the challenges of living in secular societies. Rabbi Novak's speculation that Orthodox Jews would reject civil marriage were same-sex marriages included runs counter to the Orthodox community's historical acceptance of civil marriage as an institution governed by secular society. Marriage is not a natural institution.
Marriage is an institution structured by societies.
They are a feature of civilization, not nature. Marking homosexual marriage as contrary to some natural laws is reminiscent of the justifications put forward in the U.S. for laws prohibiting interracial marriage. Moreover, all sorts of ideas about marriage have changed. Abraham ended up with a wife and a concubine, Jacob with two wives and two concubines. While surely not ideal, the rabbis of the age did not protest this use of marriage by one of their most revered teachers.