Apologetics in the public square in favor of maintaining the historic
"conjugal" definition of marriage ("one man, one woman, for the purpose
of procreation") should not be primarily the religious arguments we talk
about in our churches. It's not that we shouldn't be able to talk
about our religious views. We should! The religious liberty issue is a
different argument. What I am talking about here
is that our religious arguments are obviously not what
are going to be respected in the public square by those who do not
share our religious views. I suggest that proponents of traditional
"conjugal" marriage who are being accused of imposing their moral and
religious views on others should study the following paper, especially
noting Part II, E. The argument in the public square in favor of the
historic "conjugal" definition of marriage needs to be based on the solid
points of civil law and natural law found in this paper, and which sustained the historic understanding of marriage for millennia until this strange moment in history we call the present.
http://www.harvard-jlpp.com/wp-content/uploads/2013/10/GeorgeFinal.pdf