The research publication is here, from the Heritage Foundation. (H/T ECM)
Supporters of Proposition 8 in California have been subjected to harassment, intimidation, vandalism, racial scapegoating, blacklisting, loss of employment, economic hardships, angry protests, violence, at least one death threat, and gross expressions of anti-religious bigotry. Arguments for same-sex marriage are based fundamentally on the idea that limiting marriage to the union of husband and wife is a form of bigotry, irrational prejudice, and even hatred against homosexual persons. As this ideology seeps into the culture more generally, individuals and institutions that support marriage as the union of husband and wife risk paying a price for that belief in many legal, social, economic, and cultural contexts.
You may also want to refresh yourself on how this works out in practice by watching a debate on marriage between Dennis Prager and Perez Hilton.