I see your point, but the choices you make are based on who you are attracted to.
You still have a choice. Therefore, your sexual preference is a choice.
You and I would never choose to be in a romantic relationship with a man because we aren't attracted to men. Making that choice would make us very unhappy.
People make choices all the time that may not make them happy but they do it for whatever other reason or reasons. The point is that it IS a choice.
By the same token, homosexuals aren't attracted to the opposite sex. They could choose a heterosexual relationship, but because they aren't attracted to the opposite sex, they would be unhappy.
We make choices in life and we have to deal with the consequences of them. That does not mean we aren't responsible for those choices or that we were somehow forced to make the choice we made.
So you're saying you could choose to be attracted to men?
I'm saying you could choose to have a romantic and/or sexual encounter with whomever you wish, and that this - along with your other choices - would then define your sexual preference.
Why does someone's sexual preference matter?
I'm not sure how to answer this question. In what sense?