Here is an interesting discussion (via The Whirlpool's Rim) concerning homosexuality and the Church. I won't say anything about Eve Tushnet's excellent contribution, but you should read it nonetheless.
What I would like to discuss is an argument deployed by Luke Timothy Johnson, an argument that is both common and that I have always found problematic. Johnson argues the pro-homosexuality side. The anti-homosexuality side often appeals to Scripture and tradition against homosexuality; Johnson's counter-argument attempts to undermine that appeal by showing that Christians have, historically, sometimes overruled Scripture and tradition for other reasons. Principal among those reasons is personal experience. The cases Johnson cites are the typical ones one hears:
Slavery: Common in the Old and New Testament worlds and not rejected by Jesus or Scripture; in fact, it can be argued that the Bible even endorses slavery. Yet now slavery is universally rejected by Christians. What made the difference? What people learned through their experience of slavery and their encounter with slaves. The humanity of slaves was undeniable and it became obvious that slavery was an affront to that humanity. So in the case of slavery, Christians trumped Scripture and tradition with personal experience.
Gentiles and the Mosaic Law: The New Testament Church struggled with the question of whether Gentile converts to Christianity must follow the Mosaic Law. When it became obvious that God was working among the Gentiles in a new and unprecedented way, the Church concluded that the Old Testament Mosaic Law did not apply to Gentiles the same way it did to Jews. It can similarly judge that the Old Testament proscriptions against homosexuality don't apply to people who obviously manifest God in their lives through homosexual union.
Old Testament punishments: Although authorized by the Old Testament, no one any longer stones to death psychics or adulterers. This is another case of the personal experience of the humanity of people overruling Scripture.
The point of the argument is clear: Since Christians have changed their understanding of slavery, the requirements of the Mosaic Law, and Old Testament punishments in light of deep personal experience, so our understanding of homosexuality and its permissibility can change in light of deep personal experience. This argument, however, ignores the direction that the changes have historically taken.
The changes are generally not in the direction of increased permissibility; they are in the direction of making things more strict rather than less. This follows from Christ's proclamation that He did not come to abolish the Law but to fulfill it. More is demanded of the Christian, not less. The cases cited by Johnson show this:
Slavery: Old Testament and New Testament - permitted.
Developed understanding since then - not permitted.
Stoning for adultery: Old Testament - permitted.
Developed understanding - not permitted.
The stoning case always amazes me because everyone involved - the modern understanding, the Old Testament prophets, and Jesus Christ - are all against adultery. What is at issue is what is permissible as a punishment for adultery. As far as what is allowed as punishment, we are far more strict than they were in the Old Testament.
Mosaic Law for Gentiles: Old Testament - permitted but not required.
New Testament - permitted but not required.
This last case is really a case of no change. Gentiles were never required to observe the Mosaic Law. The question before the Apostles was whether Gentiles, in following Christ, would also be given the additional requirement of observing the Law like Jews - again, something never required of them before. The judgment of the Apostles was that such a new requirement was
So we see that the direction that change or development takes is never in the direction of increased moral permissiveness. As our appreciation for the humanity of others increases over time, the requirements for respecting that humanity (and our own) increase rather than decrease. I think there is something of an optical illusion happening here. What has really changed is our appreciation for the humanity of homosexuals, and how past persecution of homosexuals violated their integrity. So the treatment of homosexuals has come under stricter observation and regulation. It is not permissible to humiliate, harass or discriminate against them. But this doesn't mean that homosexuality is any more permissible than it was, anymore than adultery was more permissible because we stopped stoning adulterers. Authentic development always raises the bar for Christians, it never lowers it.