Conservatives generally believe, as did Durkheim (1951/1897), that human beings need structure and constraint to flourish, and that social institutions provide these benefits. In a recent edited volume on conservatism, Muller (1997, p. 7) explains:-- Haidt and Graham (Social Justice Research 2006)For the conservative, the historical survival of an institution or practice – be it marriage, monarchy, or the market – creates a prima facie case that it has served some human need. That need may be the institution's explicit purpose, but just as often it will be a need other than that to which the institution is explicitly devoted.
Muller then quotes the modern conservative Irving Kristol:Institutions which have existed over a long period of time have a reason and purpose
inherent in them, a collective wisdom incarnate in them, and the fact that we don't perfectly understand or cannot perfectly explain why they 'work' is no defect in them but merely a limitation in us. (Muller, 1997, p.7; taken from Kristol, 1978, p.161)
These are not crazy ideas. They are practical and ultimately utilitarian justifications for some of the intuitions related to the hierarchy foundation. Traditions and institutions which have been vested with authority over the ages should be given the benefit of the doubt; they should not be torn down and rebuilt each time one group has a complaint against them. (Liberals might perhaps examine their instinctive distrust of institutions and authorities, and the ways that this distrust "motivates" their own social cognition.) Viewed from this perspective, the conservative fear that gay marriage will "destroy marriage as we know it" is no longer incomprehensible – it is correct. Legalizing gay marriage would be a change to an ancient institution. We social scientists know that the institution of marriage has changed substantially over the centuries. We also know that homosexuality is not a "choice" or a disease, and we know that gay people are just as good as straight people at parenting and citizenship. We can therefore predict that in countries where gay people do get the right to marry, the new institution of marriage will be better and stronger than the old one. But it will be a change, and if social justice researchers really want to bring that change about, then they will have to understand the moral motivations that are at present working against them. Conservatives and many moderates are opposed to gay marriage in part due to moral intuitions related to ingroup, hierarchy and purity, and these concerns will have to be addressed, rather than dismissed contemptuously.