Thomas Messner at the Heritage Foundation writes about emerging threats to conscience, including threats posed by SSM:
People and groups with traditional understandings of sexual morality, including the understanding that marriage is the union of one man and one woman, face at least two types of burdens on conscience. The potential for conflicts already exists under nondiscrimination laws that treat marital status, sexual orientation, and gender as protected statuses. Redefining marriage would increase the number of conflicts.
... In New Mexico, a family-owned photography business declined to photograph a same-sex “commitment ceremony” because the owners’ religious beliefs conflict with the message communicated by the ceremony. The New Mexico Human Rights Commission prosecuted the small business under the state’s sexual orientation nondiscrimination law and demanded that it pay thousands of dollars in costs.
In Illinois, “[j]ust one month after Governor Patrick Quinn signed the civil union bill into law, a homosexual couple  filed complaints with both the Illinois Attorney General and the Illinois Department of Human Rights for the refusal of two innkeepers to rent out their privately owned bed and breakfasts for a civil union ceremony and reception.” The complaints reportedly alleged that the innkeepers violated the Illinois Human Rights Act, “which prohibits discrimination on the basis of sexual orientation by businesses open to the public.” According to one report, one of the bed and breakfasts is owned by “a Christian father of five children who has been deluged with vicious, hateful emails and phone calls.”
Conflicts like the ones in Illinois and New Mexico will only become more common if states redefine marriage or enact other legal recognitions for homosexual unions. The Becket Fund for Religious Liberty studied more than 1,000 state laws prohibiting discrimination on the basis of sexual orientation, gender, or marital status and found that more than “350 separate state anti-discrimination provisions would likely be triggered by recognition of same-sex marriage.”
Read the full report, with many more examples, here.