Ok, my thoughts on the matter. I'm going to use alot of pronouns in here, so just a warning, I'm not assigning a gender to the Almighty. I'm just using what is the common usage. I personally believe that God created both man and woman in his image, and that as such, our genders reflect two sides of the same coin.
I would say that "fake" Christians are the ones that create the greatest threat to the Christian message. When I say the Christian message, I mean the Gospel of Jesus Christ, that He was the Son of God who was sent to redeem mankind, and that regardless of what a person has done or will do, He has the power to save them. Christ never said, "I came to save to good people, the sober, the righteous, the church-going". He came and dealt with those that society considered outcasts: the whores, the taxpayers, the "sinners" (read, Greeks). He knew that the high and mighty of the religion would never accept Him.
To pervert that message into something different is completely against what he taught. In the Book of Acts, there is the clear statement that only Faith in Christ Jesus, as your savior is necessary for redemeption. Does that mean that our lives will change after the fact? Yes, to some degree. Does it mean that we fundamentally change who we are? No, our bodies and how we are wired are still the same, the way God created us. And since God doesn't create garbage, I have to beleive that the way we are wired is the way we were meant to be.
To say that God couldn't save anyone, and to reject people because they are different from you is what gives Christianity its bad name, especially true of Bible fundamentalism. They pride themselves on Scriptural knowledge, but read so much into what they see there that they miss the truth. Their own books make it clear....He is God, He has no limits, All of humanity is equal in his eyes.....gay, straight, TS, drunk, sober, whatever. To say that anyone is any better than another is legalism at its worst.
To that end I think the worst enemies of Christianity is Christianity itself. I think some preachers are going to be surprised just how many people are in Heaven, because they believed on the Son, without all their petty little prejudices. But in terms of winning people to the gospel, when you start preaching messages of exclusion, its accomplishes the exact opposite of what you are trying to do. As was noted earlier, a sincere athesist is simply an oppositionist. Someone to debate with, explain your position to, and try to win to your side.
-Angela