For this reason God gave them up to dishonorable passions. For their women exchanged natural relations for those that are contrary to nature; (Rom 1:26)
Διὰ τοῦτο παρέδωκεν αὐτοὺς ὁ θεὸς εἰς πάθη ἀτιμίας, αἵ τε γὰρ θήλειαι αὐτῶν μετήλλαξαν τὴν φυσικὴν χρῆσιν εἰς τὴν παρὰ φύσιν, (Rom 1:26)
All sins partake of the commonality of "sin." In that manner, all sins are equally damnable before God, there is no distinction in culpability between one sinner and a "greater" sinner. All sins are therefore equally forgivable under the blood atonement of Christ upon the condition of faith and repentance.
However, just because all sins are equitable in terms of damnation and forgiveness does not imply that all sins are to be seen as equal. This does not mean that we should revive the artificial Medieval (and Roman Catholic) categories of Moral and Venial sins, but just an acknowledgment that, though all sins are damnable, some sins are worse than others. After all, committing murder is worse than hating a brother, and Jesus was not equating the two in Matthew 5:21-26, but rather to show that the sixth commandment applies to the heart attitude, not just the mere physical action of murder. It is after all ridiculous to claim that hating a person is the same as murdering him. For otherwise, if one seeks the death penalty for murder, ought one to kill anyone who hates another person also? This is the type of nonsense those who see no differences at all among sins will get themselves into.
There are sins, and there are worse sins. Among the worse are what can be categorized as sins against Nature. Now, the Scriptures do not explicitly say what define sins against Nature except to give us examples like homosexuality (e.g. Rom. 1:26). Nevertheless, since "nature" (φύσις) is related to the "being" of a thing, and furthermore the context of Romans 1:18-32 has reference to Creation, it is evident that "Nature" is related to Creation. "Nature" is therefore to be defined as God's order of how things operate in their very being (ontology).
"Nature" as such has to do with God's ordained order, which is not necessarily the same as Science. Science is the study of the empirical orderliness of Nature, but it is not Nature. Furthermore, the natural world is fallen, therefore there should be some things that are in nature ("natural"), which are in fact contrary to Nature (as intended by God; Natural Law). There is also a further distinction between sins that do not violate Nature (being ethical as opposed to ontological), and sins that violate Nature (going against the established "being" of things). To the former belong sins like murder, racism, theft and so on. To the latter are sins like homosexuality, which in Romans 1:26 was stated to be "contrary to nature" (εἰς τὴν παρὰ φύσιν).
Sins against Nature are thus sins that distort the very being of things. Homosexuality, transgenderism, genderbending etc attack the created nature (ontology) of humans as male and female. Beastiality, transpecieism etc attack the created nature (ontology) of humans as humankind. The idea of creating human-animal or other types of hybrids that transcend their created kind boundaries (as opposed to species which remain their own kinds, but with one or two genes from other species) likewise attack the created nature of humanity. In fact, one interpretation of Genesis 6:1 is that of fallen angels taking human females as wives, an interpretation which I currently have no particular opinion for or against, but if that is true, it gives even greater credence to the idea that crimes against Nature are particularly heinous crimes.
Scripture does in fact speak to crimes against Nature. They are particularly heinous because they attack the very order of Creation, being ontologically rather than ethical. That is why Sodom and Gomorrah were singled out for judgment by God, not because they were the most wicked cities quantitatively, neither because they were the only ones committing homosexuality, but because they as a society celebrated homosexuality, every single one of them. Abraham had interceded to spare these cities for the sake of 10 righteous people (Gen. 18:32), but even 10 righteous people could not be found in them.
There is therefore a qualitative difference between ethical sins, and sins against Nature. While all are damnable, and all can be forgiven upon repentance and faith, sins of the latter are considered worse sins than the former. And when such wickedness is celebrated in a culture as per Romans 1:32, we know that the wrath of God is upon a society, giving them over to the wickedness of their hearts to their own destruction.