Taking the long view
In the matter of same-sex marriage (and the goodness of gayness generally), the progressives see conservatives as worthy of the same odium now attached to the white supremacists of days gone by -- such that those who partook even of the casual, and mostly passive, racism endemic in our society once upon a time can no longer be seen as having anything worth saying on almost any other subject; their racism taints everything they have to say. The progressives accuse their opponents of like bigotry, and seek to hammer them into submission or silence their voices. The conservatives are "on the wrong side of history," they say.
But to conservatives like me, the progressives appear very much like the Nazis and their supporters in the German Christian movement, who followed "positive Christianity" -- a program of eliminating ancient ties to Judaism as well as the supposed flights of non-scientific fancy such as the Apostles' Creed, leaving only a Christianity of values: values which were to be fully subordinated to the new value of German identity and to the idea of the Führerprinzip.
The Nazi takeover of the Church in both ideology and governance won the day in their society and was widely supported. Those who refused to cooperate, such as Dietrich Bonnhöffer, were seen as cranks -- though we now see them as martyrs and confessors; meanwhile, the collaborators excuse their shameful acts and say they were done by somebody else, and if one were to be known as a vocal supporter of the German Christian movement today, pretty much anything else he or she stood for would be discounted as issuing from a polluted source.
So you pays your money and you takes your choice when decreeing which side of history is the wrong side. Those who win the argument today may well be objects of scorn and shame in years to come.