One of the clearest dynamics in the polls is that married Americans are much more likely to oppose ssm than single Americans. Married people don't have some special fear or hate for gay people. Most of us oppose ssm because the logic supporting ssm imposes an system of morality that is adverse to ours, and defines our relationships, our sexuality, and our identity in crass and demeaning terms.
Rather than just crafting an exception to the rule and "letting same-sex couples marry," the Goodridge court redefined marriage according to its new paradigm. By sanctifying this faddish theory of marriage as a manifestation of "sexual orientation," the Goodridge court not only redefined our most treasured institution, but redefined the sexual identity of every person who has married or wants to marry. The message is that it's morally "wrong" and "discriminatory" celebrate the special ness of the union of the sexes and that we should change our world view. This suggestion seems to me as judgmental and intrusive as the right-winger's suggestion that a gay man needs therapy to change his sexual orientation.
I hope that at some level you can understand why the majority of Americans who oppose ssm are unwilling willing to have our sexual identity redefined by a few folks who think they know what is best for us.
America is big enough to play host to different ideologies. For example, US regulations define multiple categories of food, including "dolphin-safe," "organic," "halal," "kosher," and another kosher-like category for a different Jewish group whose rabbis defined Kosher differently. The idea is that when you create a different category, you give the category a different name. You don't need to overwrite one set of criteria that has one purpose, with a different set of criteria with a different purpose. If some reform or renewal Jewish rabbis decide they want certain types of bacon cheesburgers to be "Kosher," it would be wrong for them to pressure the courts to change an existing category; they should ask instead for a new category, in order to protect food labeling for their own group.