Stop Same Sex Marriage
... the term. By delineating it with its own term, you imply that it's somehow different than "regular", heterosexual marriage. The gay and bisexual couples I've met in my professional and personal life have had relationships just like I've had as a heterosexual male. Using the term same-sex marriage to me implies that it's different, and should be treated differently in the eyes of the law, the same way that any hyphenated-American automatically separates that group of people from an unbranded American.
Either you're married or you're not. Either you're American or you're not. Any additional qualifiers are just noise designed to distract and confuse.
Should certain groups of people be prohibited from getting married? Swap out any term and see how well it flies.
Should black people be prohibited from marrying? Same-race marriage.
Should elderly people be prohibited from marrying? Same-age marriage.
Should poor people be prohibited from marrying? Same-economic-status marriage.
Should Catholic people be prohibited from marrying? Same-religion marriage.
Want to start changing minds? Start by changing your own. Eliminate the confusion around marriage and the term same-sex marriage by not using that term any longer. Call it what it is.