"Because marriage is central to family life, it has a
political dimension. As I discuss in my book Moral
Politics, conservative and progressive politics are
organized around two very different models of married life:
a strict father family and a nurturing parent family."
[...]
"When conservatives speak of the 'defense
of marriage,' liberals are baffled. After all, no
individual's marriage is being threatened. It's just that
more marriages are being allowed. But conservatives see the
strict father family, and with it, their political values
as under attack. They are right. This is a serious matter
for their politics and moral values as a whole. Even civil
unions are threatening, since they create families that
cannot be traditional strict father families." --
George Lakoff,
"What's in a Word?"