Thanks, Ollie, for your detailed and interesting post. I'm sorry it took me awhile to respond. I have a couple of comments.
I'm a little late responding to this because I missed it earlier today. I apologize.
First regarding the immediate literary context of the verses quoted. Looking at Romans 1:18-32 overall, it still seems to me that same-gender sex is categorized along with other sinful activities. Verses 26 and 27 are in the midst of a broader passage describing the sinfulness of humanity and our need for salvation. Given the context, I would hesitate to extrapolate a great deal from similarities to Greek philosophy; Paul himself, whatever his influences, framed the issue in the context of humanity's descent into sin.
Not exactly. It was not the sinfulness of humanity, it was the sinfulness of the Gentiles. Paul was copying the style of a form of Jewish literature which had become popular during the preceding two centuries. It blamed all the ills of the world on the ascendancy of the pagan Gentiles (for which read the Greeks and Romans), and their sins, which all spring from their rejection of the One God. The most easily obtainable example of this "apocalyptic" literature is found in the 14th chapter of
The Wisdom of Solomon.
The Christians in Rome could see the interplay of these pagan sins, especially the ones that Paul focused on, on display daily in the palace and the homes of the elite. They would be agreeing that the sins of the pagans were terrible, and thankful that they had been saved from their degradation. Then we get to Chapter 2, verses 1-3:
"Therefore thou art inexcusable, O man, whosoever thou art that judgest: for wherein thou judgest another, thou condemnest thyself; for thou that judgest doest the same things. But we are sure that the judgment of God is according to truth against them which commit such things. And thinkest thou this, O man, that judgest them which do such things, and doest the same, that thou shalt escape the judgment of God?"
Paul goes on to show that being a God-fearing Gentile is not enough to save you. Nor is being a Law-honoring Jew enough to save you. And he chooses different sins to highlight for each group. He is saying that it does not matter that your sins are different from those of another group:
all have sinned and come short of the Glory of God.
So, yes, Paul does describe the sinfulness of humanity , but he does so in stages, and that for a specific purpose. Verses 1:18-32 do not describe the fall of humanity in general, it describes the specific fall of the Gentile pagans.
In this context, it becomes clear that he quoted Plato in order to show that even in their Godless condition, the Gentile pagans recognize that some of what they are doing is "
para physin" or sin. Since it their own self-recognized sin, it needs to be understood as they understood it: uncontrolled passion with no regard as to who or what is the object of the passion. The same-sex aspect of the example was mainly an ethnic joke against Cretans in general, and one of the other participants in the dialogue in particular. It was also an easy way to signal that the participants were going overboard in their addiction. In Greek society, sex, whether with women or with youths or other men, served certain purposes, and should only be "enjoyed" when it was appropriate to those purposes.
My second comment is a reminder to those of my position that same-gender sex is far from the only sin mentioned in this passage. Immediately following on the passage I cited, Paul says "Therefore you have no excuse, whoever you are, when you judge others; for in passing judgment on another you condemn yourself, because you, the judge, are doing the very same things." (The following verses continue this thought.) I want to make it clear that I do not see same-gender sex as something qualitatively different from all other sins. I do not believe it is judging to discern and teach what scripture says on any particular issue, but it would be judgmental to condemn others while I hold myself to a looser standard. I think Romans 1 tells us something of God's standards for holiness, but it also makes the point that none of us is righteous on our own. While this is not a license to overlook sin, it is likewise not a license to forget that it is but one sin of many.