I've never heard an LDS authority say that actual same-gender attraction is a choice. Maybe it is, maybe it isn't, I don't know. 
 
What I do know, however, is that everyone has the choice to choose whether or not to act on those attractions. The church teaches that individuals should not. It might be a serious challenge for them, but it's not impossible. Everyone can overcome temptation. 
 
We believe that marriage is between a man and a woman not because we want to discriminate, but because we believe that it is part of God's plan in the afterlife and in the eternal perspective, and marriage between a man and woman is a very sacred part of that plan.