When the Supreme Court struck down the Defense of Marriage Act, the justices opened a number of doors -- including extending the protection of the federal Family and Medical Leave Act to many same-sex married couples, so they are no longer forced to choose between caring for their spouse and keeping their job.
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.