Hasn’t there been constant opposition to homosexuality throughout Christian history?
Recent and detailed historical scholarship questions that claim. Although one could find some opposing voice in every century, there was no common opposition to homosexuality in Christian Europe until the late 12th century except for a period around the collapse of the Roman Empire. Indeed, for nearly two centuries after Christianity had become the state religion, Christian emperors in Eastern cities not only tolerated but actually taxed gay prostitution. In 7th century Visigoth Spain, a series of six national church councils refused to support the ruler's legislation against homogenital acts. By the 9th century almost every area in Christian Europe had local law codes, including detailed sections on sexual offenses; none outside of Spain forbade homogenital acts. By the High Middle Ages, a gay subculture thrived, as in Greco-Roman times. A body of gay literature was standard discussion material at courses in the medieval universities where clerics were educated.
Opposition to homosexuality, as in Augustine and Chrysostom, rested on reasons unacceptable today: "natural-law" arguments based on beliefs about supposed sexual practices among hares, hyenas, and weasels; a philosophical Stoicism that was suspicious of any sexual enjoyment; a sexism that saw a degrading effeminacy in being the receptive partner in sex. All-out Christian opposition to homosexuality arose at a time when medieval society first began to oppress many minority groups: Jews, heretics, the poor, usurers. A campaign to stir up support for the Crusades by vilifying the Muslims with charges of homosexual rape also played a part in Christian Europe's change of attitude toward gay and lesbian sex. See John Boswell, Christianity, Social Tolerance, and Homosexuality.
Taken from Daniel A. Helminiak, FAQs: Catholicism, Homosexuality, and Dignity, written for DignityUSA, 1996, 2000.