Just as I can't understand Christian women, I can't understand Christian LGBT either.
I have been told by some Christians that, actually, the Bible does not say anything wrong about homosexuality, but maybe they misunderstood me and thought I was talking only about lesbianism. Bible does not care much about women's sexual preferences, probably because it doesn't care too much about women's sexuality in general - as long as they're caste.
Anyway, on with the "Bible says nothing about gays" thing.
Thou shalt not lie with mankind, as with womankind: it is abomination. Leviticus 18:22
I think it's pretty clear, isn't it? By the way, have you realized that it's written as if addressed to men, not men and women? Almost like the speaker - supposedly, God Himself - didn't care who women lie with.
I have seen people saying that Leviticus is "about classifying things" and that this verse is not about sex. Well, actually this whole chapter is about sex. I invite everyone to go and see it. Leviticus is God telling rules to Moses, and this chapter starts defining what's incest - unless you want to be literal and think it's about seeing people naked. And just after the gay part, it forbids to lie and defile yourselves with beasts...
Maybe this one is clearer:
If a man also lie with mankind, as he lieth with a woman, both of them have committed an abomination: they shall surely be put to death; their blood shall be upon them. Leviticus 20:13
Death. Just like that.
What could we expect, if cross dressing is also an abomination
The woman shall not wear that which pertaineth unto a man, neither shall a man put on a woman's garment: for all that do so are abomination unto the LORD thy God. Deuteronomy 22:5
Just like in Christian Women we would like to believe this is all the Old Testament and that the New one is far more liberal.
What happened with women about the old/new testament lack of differences happens with LGBT too. Let's start with what the apostle Paul says to Timothy
Knowing this, that the law is not made for a righteous man, but for the lawless and disobedient, for the ungodly and for sinners, for unholy and profane, for murderers of fathers and murderers of mothers, for manslayers, For whoremongers, for them that defile themselves with mankind, for menstealers, for liars, for perjured persons, and if there be any other thing that is contrary to sound doctrine; 1 Timothy 9-10
"The law is made for the sinners, such as those who defile themselves with mankind." The apostle Paul also writes letters to the church of Corinth:
Know ye not that the unrighteous shall not inherit the kingdom of God? Be not deceived: neither fornicators, nor idolaters, nor adulterers, nor effeminate, nor abusers of themselves with mankind, 1 Corinthians 6:9
In the letter to Romans, he complains that
And likewise also the men, leaving the natural use of the woman, burned in their lust one toward another; men with men working that which is unseemly, and receiving in themselves that recompence of their error which was meet. Romans 1:27
I love when I see a verse I don't know where to start with. On one hand we got that "men burned in their lust one toward another", and just before, the "leaving the natural use of the woman", as if the natural use is to satisfy men's lust.
In the next verses Paul goes on a rant
And even as they did not like to retain God in their knowledge, God gave them over to a reprobate mind, to do those things which are not convenient; Being filled with all unrighteousness, fornication, wickedness, covetousness, maliciousness; full of envy, murder, debate, deceit, malignity; whisperers, Backbiters, haters of God, despiteful, proud, boasters, inventors of evil things, disobedient to parents, Without understanding, covenantbreakers, without natural affection, implacable, unmerciful: Who knowing the judgment of God, that they which commit such things are worthy of death, not only do the same, but have pleasure in them that do them. Romans 1:28-32
The last verse is specially funny: knowing that to God, that kind of people is worthy of dead, not only they do, but they like it.
So, I hope it was brief enough what reasons have the Bible for LGBT not to be Christian. Please, to all LGBT people and all who respect them: do you see why you shouldn't claim to be Christian?