So the question at stake is only whether homosexuality is harmful or disordered, right? Your whole case rises and falls on the belief that it is harmless, just as mine rises and falls on the belief that it is harmful. Do we agree so far?
Homosexuality
per se is neither harmful nor contradictory to natural order or law. That seems self-evident to me; "defective" people shouldn't breed, but they shouldn't be alone (Ge 2:18). Using a version of natural law, one could make an argument that we should not give heterosexual type 1 diabetics insulin, but let them die because allowing them to live beyond childhood to procreate will result in harm to society (more type 1 diabetics via procreation) and is disordered and against natural law (they would die naturally if left to themselves without insulin). It seems disordered and harmful to mess with natural selection in many cases, but people do, choosing to follow what they perceive is the higher natural law or that "crazy thing called love."
I don't believe my position rises and falls necessarily on biological determinism being the cause of homosexuality, but it is unassailable, in my opinion, if it is the cause. Science is slowly proving what should be self evident to any person who cannot choose to be attracted to, or fall in love with, the same sex--
homosexuality is biologically determined. It is fundamental that God's justice account for biologically determined factors, and that is evident by example in the Book of the Law of Moses (e.g. sin offerings for menstruation, cities of refuge, David eats the Holy bread, etc.).
To briefly address the scriptures and the words of God: Homosexuality
per se is not condemned in scripture. Rather, its general condemnation has been read into scriptures that are not about homosexuality
per se, if about homosexuality at all in some cases. I suggest you read
The Church and the Homosexual by McNeil (Catholic scholar using Catholic sources), which does an okay job of addressing the mistranslations and misinterpretations of most of the scriptures presumed to be about homosexuality
per se. But the overriding principle is this: Matthew 7:12. That principle is not violated by two woman loving each other and uniting as a family, whether that relationship involves sexual intercourse or not.