The truth of God and the Universe typically, in my view, lies somewhere in the middle of what science or religion has to say about it. Some Christians would argue that God made men and women different to fulfill the role of biological procreation. Most scientists would agree although many would find God an unnecessary addition to the equation.
However, when it comes to homosexuality where the supposedly God given orientation of sexual interest appears to not fit in with the plan for sex taking place in the context reproduction of the human species and of an exclusive life long partnership of caring and loving and mutual sexual interest not brought on by some other psychological disorder (according to the APA), then some Christians cry foul (sin) and condemn "the behavior".
Unfortunately for those Christians more and more science is demonstrating the nature of God's creation and forcing rational people to change their minds about their understanding of God's Will. I came across an article on CNN which describes the result of a study which further indicates the genetic or congenital nature of homosexuality:
Having older brothers tied to being gay, if you're a guy - CNN
Apparently statistical analyses have pointed to an increased likelihood that men with older brothers would turn out to be gay. Such studies led back to the experience of the mother as the likely cause for the increased chance of a child to have a genetic configuration for homosexuality. In these cases homosexuality cannot be a sin as it is a genetic identity and as such for those of faith, a God given trait of that person.
On the science side of things this brings up a challenge for many who see evolution operating exclusively through the DNA and its random mutations. Here it is the presence of anti-bodies in the mother's blood due to a previous experience of the mother (giving birth to a male) that alters the genetic (or genetic expression) of the next male child in her womb. This shows that the experience of an organism can influence the gene level characteristics of that organisms offspring. This breaks the rule that only random mutation is important but the environmental experience of the parent can also be important to the character of the offspring.
This kind of Lamarckism is often derided by evolutionists but it appears that there are scientific studies which are uncovering some Lamarckian mechanisms for evolutionary development. Perhaps these mechanisms can help reduce some of the speed of species development issues that are evident and that "trouble" evolutionary biologists. Trouble, of course, in the sense of evolutionary biologists love such troubles as they are often a short route to great advances in evolutionary theory and not as some creationists try to pose them as fundamental problems for evolutionary theory.
So between homophobia and strict non-Lamarckism lies the truth about what I would call God's plan for us, that we be diverse (Tower of Babel), fruitful and have dominion over the Earth. Often our punishment is our reward in humanities' pursuit of knowledge, a sentiment shared by many religions with respect to the price and privilege of the advance of human knowledge respecting nature and God's creation. What is sin from one perspective (homosexual marriage) is a blessing from another (the basis for a family without the necessity of adding more people to a rapidly over-populating planet.
God is more subtle than any Biblical interpretation or scientific theory can fully describe, but we can use both in sync to help us have meaning and lead better lives.