I would have to disagree that homosexual attraction or orientation is not a sin but homosexual behavior is a sin. St Paul tells us in Romans 1 that homosexuality is against nature and by default an act of lawlessness.
Oh did he now?
Romans 1:26, 27:
"Because of this, God gave them over to shameful lusts. Even their women exchanged natural sexual relations for unnatural ones. In the same way the men also abandoned natural relations with women and were inflamed with lust for one another. Men committed shameful acts with other men, and received in themselves the due penalty for their error."
Actually, he is clearly referring to lust and actions. If I'm attracted to women, am I sinning? What about if someone is attracted to members of the same sex? How about Fr. Seraphim Rose, who was gay, yet didn't exercise his feelings and didn't entertain his desires?
Is this not Orthodox theology?
No, as who you are attracted to is not something that can be sinful. But acting on that, and entertaining lustful thoughts is what is sinful.
What Fr. Seraphim Rose sinning on his deathbed just because he was attracted to other men? It's just absolutely stupid to say that your sexual orientation is a sin. It's a product of the "uck" factor that people feel, and this false assumption that it's impossible to be born gay.
What? Is heterosexuality the only non-sinful orientation? Should all homosexuals be driven into heterosexuality? Will they only be repentant then?
No, as I said before. Orthodoxy teaches that it is the lust, the thoughts and the actions that determine if you are sinning. It isn't your state.
Being born homosexual is no different than a little child who is born addicted to crack. Yet that little child has committed no sin, and would receive a full Orthodox funeral if he dies before his baptism and dies at a young age. However, that little child, as he grows up, will indeed sin if he actually abuses drugs, acting on his addiction.
Same for those addicted to nicotine. People who don't smoke anymore, or who don't drink anymore, but who are still addicted to nicotine and alcohol aren't sinning just by being addicted. They would sin though if they smoked, or if they got drunk.
Our Church makes a strong distinction between a person's fallen psychological, physical state that is often unalterable, with any thoughts and actions that might result from their fallen nature.
Also, the fallen nature that results from the ancestral curse doesn't mean you have sinned. Yet it makes you a fallen being with a tendency to sin, an inevitability of earthly death and in need of salvation. Look at the Holy Theotokos, she was born a fallen human being, but never had any personal sin despite being born a fallen human being.