Yes, Nero declared himself married twice. No law legalized any such union, and his peers mocked him for it...http://en.wikipedia.org/wiki/H istory_of_same-sex_unions
Amongst the Romans, there were instances of same-sex marriages being performed, as evidenced by emperors Nero and Elagabalus,who both supposedly married men, and by its outlaw in 342 AD in the Theodosian Code, but the exact intent of the law and its relation to social practice is unclear, as only a few examples of same-sex marriage in that culture exist.
So gay marriage wasn't something prohibited until the Theodosian code of 342.
Ask yourself this question. Why, in ALL of human history, apart from ANY religion or culture, homosexual marriage has never been accepted in a single culture from start to finish?
Even though there are extremely rare and brief glimpses, it has never established itself and spread. Can't make a bigoted blame on the Catholic Church, can you?