I have a lot to say about this subject.
First, I have a background in psychology, and research is coming out that SOMETIMES homosexuality is biologically deteremined. For example, a pregnant woman who is under a lot of stress during her pregnancy will have waves of testosterone washing over the baby--now if that baby is a girl, she is more likely to be born with gender identity disorder. Her choice? I think not. A result of sin? Absolutely! Also, homosexuality runs in families--evidence to the "nature" side of the controversy. Still, though, and deviation from perfection is not part of God's plan, and he certainly is not pleased with gay-bashing, discrimination, isolation, low self-esteem, etc. etc. and all the other difficulties that result from homosexuality.
On the other hand, our sex-laden culture has desensitized people to sex and homosexuality, and more and more young people are "experimenting" with homosexual behavior and deciding that they are "gay" or "bi". This is a problem with our cultural media.
The reality is that one verse is repeated 5 times in the Bible. It is "for this reason a man will leave his father and mother and be united to his wife. And they will become one flesh." That is where God draws the line. When we start pushing the line we end up with promiscuous sex, orgies, pedophilia, incest, homosexuality, beastiality, etc. etc. etc. THIS IS WHERE GOD DRAWS THE LINE, AND HE DRAWS IT THERE FOR GOOD REASON!!!
With that said... I do not take it upon myself to preach this message to homosexuals. (I am only posting it here because I think my perspective is a little different than the "standard" answer, and I thought you all might be interested in my take.) The message I preach to homosexuals, liars, cheaters, murders, rapists, drug addicts and sinners of all kinds is that Christ LOVES them and wants desperately to have a relationship with them!!! Any person who does not know Christ must be told this message first and foremost: Christ died for you because he loves you!
As for a person being a "gay" christian, I am thrilled that a gay person feels courageous enough to face the "lions" in church who can be hateful and persecutory towards them--and I know there are many
Personally I don't take it upon myself to preach to them about the "wrongness" of their lifestyle UNLESS they are acting promiscuously and not in the manner befitting to a Christian. If they are in a "healthy" relationship with a same-sex partner, I will leave it to God to convict their heart. Maybe we will have conversations about it, but I do not take it upon myself to do the work of the Holy Spirit.
Thanks for reading all this. Be blessed