For me, either side of the nature/nurture argument is unproductive. If it were definitively proven that alcoholism is genetic, then I have a perfect excuse ("I was born this way") for my compulsion. If on the other hand, it can be shown that the behavior is purely learned, then I can convince myself that it can be "unlearned" and controlled. Either path will be to my detriment, and consequently it's an argument I tend to avoid altogether. My personal experience and observation of others indicates that alcoholism can be successfully dealt with and managed when viewed as a spiritual shortcoming, and I suspect homosexuality is similar.
In that regard, I pity homosexuals, not only because of their malady, one which I believe I can identify with through my alcoholism, but because there is an agenda out there pushing society to accept and embrace it. Legitimizing gay marriage creates a protected class and provide social sanction and forced acceptance of a behavior similar to finding that public drunkenness laws should not apply to alcoholics. They are deviant behaviors, and excusing, or even elevating them will only result in more of them, much to the detriment and heartbreak of the people who indulge in them.
I have frequently thought of homosexual behavior in terms of an addiction, like alcholism. I appreciate your insight.