I was reading the wording for a bill passed recently, im not sure whether it was state or what, but it legalized gay marraiges. most conservatives were fighting it with this idea: the exact same wording of the bill could also be used to explain and legalize every sort of marraige or sexual act.
some people find gays to be disgusting, some don't. many consider a fifty year old marrying a 12 year old to be disgusting, a few don't. brother marrying sister, father marrying daughter, age differences, who knows, specie differences (!?), all could happen eventually, and legalizing gay marraiges would be the first step toward that. if the government is saying "your personal life, who you choose to have sex with and get married too is the business of the partners and no one else", well, it can go so many ways....
which isn't to say i don't support it, i do. but still...