While Scalia's point may be historically correct, it is in no way a justification for upholding DOMA. Indeed, even if DOMA's sole purpose was to remain true to history, its effect was to deprive gay couples of rights and privileges enjoyed by other legally married couples for no other reason than that they are gay.
Many of us (Christians) think we should voice our objections if we hear or see something we perceive to be immoral according to how we interpret the Bible. And we often do this without being asked, without having a relationship that gives our opinion context, without knowing where the other person is coming from.
While my own anecdotal experience is that gay relationships are very stable, it's inevitable that some gay couples will be unhappy and will want to divorce. As that occurs, gays will need to have access to the same legal support that straight couples have had and will need equal consideration in court.