Anom, I began having a strange and unexplainable attraction to girls when I was in 4th grade. Nobody taught me to feel that way. I was the oldest child so I didn't pick it up by watching an older sibling. And, since I was a little early in that particular aspect of childhood development, I didn't even have any friends who talked about it.
It was not my choice.
Now, why, if I had no choice in my "staightness" would I have any reason to believe that homosexuals have chosen what gender they're attracted to any more than I did? Moreover, the gay men to whom I've talked tell the same story of early, unexplainable attraction -- but to men instead of women.