There's been a thread on this if you want to read it.
I personally lean towards the psychological explanation. Inherent traits tend to have very little to do with any preferences and desires. A very large chunk of a person's behavior and mental processes are the result of what they've learned or experienced. I don't know exactly what factors cause homosexuality, nor do I know when after a person's birth are a person's sexual desires even formed. I can't say for sure there are no genetic factors though, so I won't dismiss it entirely. Sexual preference is 85-90% psychological and 10-15% biological imo.
What a person learned from this reinforcement and punishment could remain in a person's subconscious for his entire life potentially deciding who he is attracted to and what he percieves as good or bad. There probably aren't any definitive evinronmental factors that for sure causes certain sexual preference though. Considering how complicated and bizarre the human mind is, I'm pretty sure the cause of sexual preference is also complicated and perhaps bizarre. I think sexual preference is caused similar to most preferences of our mind; that is, we learn behavior and form beliefs, personalities, values, etc. as a result of what we learn in life.
This does not mean that I think homosexuality is a choice though, at least not a conscious choice. Homosexuality is no more of a choice than a person's favorite color or favorite music genre or favorite hair color imo. Obviously, people aren't born with these preferences, thus the causes of those are mainly psychological, but that doesn't mean it's a conscious choice. I would say that it's a subconscious 'choice.' Essentially, a variety of factors combine and collide inside a person's mind and it eventually makes them desire certain things over another.
I personally don't think it's biological, at least not for most people. People don't even have an understanding of gender until after birth, much less any attractions to any specific genders. Likewise, I don't see how people would already have sexual preference before they can even understand the difference in genders. How does that work?
