“The intimate coupling of two men or two women is not marriage. It is a pale and misshapen counterfeit that will only serve to empty marriage of its meaning and destroy the institution that is the keystone in the arch of civilization … Marriage is the sine qua non for healthy children and a stable society. It is 'fundamental to the very existence and survival of the race'…”

Fern Britton Meets John Barrowman BBC 2012

Context: I don't think the issue's about being against gay marriage. It's about being for traditional marriage and articulating the reason that's important. You have to have a basic family structure. There's never been a civilization that has rewritten what marriage and family means and survived. So there is a sense in which, you know, it's one thing to say if people want to live a different way, that's their business. But when you want to redefine what family means or what marriage means, then that's an issue that should require some serious and significant debate in the public square.

page 4
Dark Rooms (2002)

Actually from 1969 leaflet by The Feminists, "Women: Do You Know the Facts About Marriage?". Its text was reprinted in the anthology Sisterhood is Powerful edited by Robin Morgan.
Misattributed

United States v. Windsor oral argument,

Is Divorce Wrong? (1889)
Context: Marriages are made by men and women; not by society; not by the state; not by the church; not by supernatural beings. By this time we should know that nothing is moral that does not tend to the well-being of sentient beings; that nothing is virtuous the result of which is not good. We know now, if we know anything, that all the reasons for doing right, and all the reasons against doing wrong, are here in this world.

Source: Sylvia cartoon strip, p. 21