Romans 1:18-32 has been one of the primary battlegrounds for how Christians should view homosexuality. As with other passages I've examined in this vein, knowing the context and culture sheds light on how these verses should be understood, but this context and culture has to be understood correctly in tandem with the words which Paul write. When discussing Paul's worldview in Romans 1, many opt for what I would call a culturally-bound, mythic argument. Myth in this sense is anthropological and literary, not factitive or historical. It’s not a fairy tale or a fiction; rather it is an archetypal story which explains how a group perceived and explained some aspect of their world.
To understand this better with an example, ponder what comes to mind with the phrase "the American dream." We Americans we have a lot of our own myths, our own archetypal stories which help us explain the world. When we talk about living the American dream, we describe the opportunity available to every American through hard work and diligence to obtain a certain level of socio-economic status. What came into your mind were constituent components of that myth. The same situation is in operation here when discussing Romans 1. Many people argue that you cannot understand Paul’s argument unless you recognize that he is expressing a common Jewish myth about the origins of idolatry and its effects on the world.
Here are the components of that myth: There was a time when the entire world was monothestistic and one set moment in time when polythesim and idolatry came into the world. Up until that one moment there was no such thing as homosexuality. The Gentiles were responsible for the introduction of idolatry, so there was no homosexuality among the Jewish people. Were there to be no idolatry in the world, all homosexuality would disappear since idolatry is the cause and homosexuality a consequence. Those who argue that this myth undergirds Paul’s argument here challenge the more traditional interpretation of this passage, positing that Paul’s thinking on the matter of idolatry is bound up with the argument; if we recognize that that thinking is fallacious, the rest of the argument falls to the ground. They also argue that Paul simply doesn’t have the same categories we have regarding sexual orientation and activity; thus Paul is hopelessly outdated, talking about categories that don’t exist in our world. Consequently this passage has no applicability to homosexuality today.
The problem with this culturally-bound, mythic argument is two-fold. First, it is comprised of constituent parts which are never found expressed as a composite whole anywhere in Jewish literature. Much like Bultmann's gnostic redeemer myth, this myth is a modern construct that can only be supported piecemeal, not en toto. This is an example of two common scholarly errors: parallelomania and dependent hypotheses. Second, even in this expression of the myth, its arguments do not account for the entirety of Paul’s thought in Romans 1, nor do they necessarily vacate the logic of his argument, which is concerned with human sinfulness in general, not homosexuality in particular.