But, if I could at least make an attempt, I'd say that those same Christians make the argument that A) abortion is harmful to children and B) (since the prime goal of marriage is the establishment of families) gay marriage is also harmful to children
Logically then, they are not hypocritical in that they don't
beleive the Government should tell people what to do with their lives and in that they don't believe people should harm others.
Even so, you would contend that both A and B are false. But, on a beleif level, its not nescessarilly hypocritical since they are only advocating a ban on actions they beleive to harm others.