My opinion, which differs from the popular idea, is that sexual orientation is not something you cannot change. And I am a Christian who believes the Bible. And the Bible says that homosexuality and such things are a sin, so that if you want to be a Christian, and want to go to Heaven you have to stop doing that. I also know that having a gender change won't change anything about the gender you were born as, which is in your entire body and soul.
I sometimes try to tell these things to people, because I believe it is the truth. Of course I will not force anybody because that's a choice they have to make themselves. All you can do is tell them--in the nicest way you can.