There were those in Paul’s day who “worshiped and served the creature rather than the Creator” (Rom. 1:25). Such seems absurd to us that anyone would do that, but look around. Are there some individuals today who, exchanging the truth for the lie, have chosen to serve the creature (even their own wants and wishes) rather than the Creator (with His wants)?
If it is wrong that man “exchanged the glory of the incorruptible God into an image made like corruptible man” (in Romans 1:23, regardless of the culture), and if it is wrong that man “exchanged the truth of God for the lie” (in Romans 1:25, regardless of the culture), then would it not be equally as wrong (in the sight of God) when that same man “exchanged the natural use [of the male/female] for what is against nature” (in Romans 1:26, regardless of the culture)?
Male-male relationships and female-female relationships are “against nature” and “shameful” — not because they are against some cultural norms (that ebb and flow from culture to culture), but because they are against God’s culture/nature (which is the only one that matters, for it remains constant).