Most christians I have seen arguing on the internet for the immorality or sinfulness of homosexuality tend to start out with the OT laws as their reason, and only once that futility has been pointed out a number of times do they turn to Paul (or 'Paul') who, as just demonstrated, is equally futile to turn to.
That is my experience too.
It's worth pointing out that the obsession on the part of
some modern Christians with homosexuality is a very modern thing. For comparison: I know of only one Christian text from the Middle Ages on the subject of homosexuality - the famous
Liber Gomorrhianus by Peter Damian. And in that book, Peter Damian doesn't actually attack homosexuality per se. He's writing about homosexuality
in monasteries, which he condemns at enormous length. In fact if he's to be believed then eleventh-century monasteries operated something like Old Compton Street. But at no point does he actually argue that homosexuality is intrinsically wrong for everyone. He probably would have thought that if you'd asked him about it, but he doesn't say it. Why? Because people in those days didn't care very much about the subject.
I just participated in another thread where oral sex is considered sinful by one of the participants. Is there any biblical backing for this?
Not that I know of!
Actually, there are a number of places in the Bible that condemn fornication - ie sex outside of marriage. And saying that the Bible condemns a bunch of stuff doesn't help, even Jesus preached against sexual sin as it was understood. And for the first nearly 2000 years of Christianity homosexual behavior was synonymous with fornication because the idea of same sex marriage is a very recent one.
I don't think there is any text in the Bible that condemns sex outside marriage. I know there are a couple of passages in the New Testament that attack "fornication" - but the word that is commonly translated "fornication" there is actually "porneia", which simply means non-specific sexual immorality. And indeed there are some passages, such as parts of the book of Ruth, which seem implicitly to commend sex outside marriage.
Again, the obsession on the part of
some Christians with sex outside marriage is a modern thing. I know of only one ancient Christian author who said that sex outside marriage is wrong, and that's Clement of Alexandria. But he also said that it's wrong to have sex before dinner, that it's wrong to ask other people to pour the bath water over you, and that it's wrong to laugh too much (this is all in his
Paedagogus). In other words, he was describing the sort of lifestyle he believed to be fitting for a Christian, rather than laying down hard and fast moral laws.
In the Middle Ages, people weren't bothered about sex outside marriage much at all. For people on the lower rungs of society, marriage would rarely have occurred at all - people would just start living together and call themselves husband and wife without going through any ceremony. Think of Abelard and Heloise (and
he was a theologian), or just read Chaucer. The same is true of the Renaissance and early modern period - just read Shakespeare. Enormous amounts of naughtiness without the slightest indication that it's wrong. Or read Boswell, talking about his activities with prostitutes by night and discussions about theology with Johnson by day.
The traditional Christian view, in late antiquity and the Middle Ages alike, was that sex
in general was (not wrong, but) a basically bad idea. Marriage was regarded as acceptable but a lower state than remaining single. Married Christians in late antiquity often lived together chastely, or even separated and became monks or nuns, because they thought that sex, even inside marriage, was to be discouraged. This remained the prevailing attitude for many centuries, but I think it tended to be restricted to more zealous people. In early modern times, this attitude became particularly associated with the Puritans, and I believe that they are the ones who really made the distinction between sex inside marriage (acceptable) and outside it (unacceptable). The enormous influence that Puritanism had, both in its own right (especially in America) and as an influence upon Pietism and Evangelicalism (especially in Europe), helped to spread this view. The result was that by the late eighteenth and early nineteenth centuries, the notion that sex outside marriage is wrong had become very widespread and increasingly mainstream. It was of course subsequently an important element of "Victorian values". Modern evangelicalism and allied movements retain it. So, today, the view that sex outside marriage is wrong is especially dominant among evangelicals and fundamentalists, and also Asian Christians (because of the influence of Confucianism). But it's really a modern development within Christianity and one that, although no doubt it always existed to some degree, was far less important in the past. Which is why there are plenty of Christians today who also eschew it. This is especially so among theological liberals and on continental Europe, where evangelicalism has never been very popular. There are even Christian swingers.