Extramarital sex wrong? Gays and supporters of same sex marriage less likely to think so
One of the arguments against same sex marriage is that it will fundamentally weaken the institution by opening it up to groups who do not take the vows as seriously as they should, thus cheapening the whole enterprise and leading more people to forgo it entirely. Stanley Kurtz is probably the most widely known advocate of this view. Of specific interest to this post is the following excerpt:
Many thoughtful gay activists see same-sex marriage as a chance to redefine marriage itself — stripping marriage of what they see as its outdated and constricting connection to monogamy. And of course, even more powerfully than openly non-monogamous gay marriages, legalized group marriage would destroy the taboo against adultery.