Not going to try to challenge any religious beliefs -- I'm Christian and fully support gay marriage -- just wanted to point something out.
While you may interpret one of the bible verses prohibiting marriage, look at what else it prohibits.
Pigs - Leviticus 11:8 - "You must not eat their meat or touch their carcasses; they are unclean for you."
Polyester / other fabric blends - Leviticus 19:19 - "You are to keep My statutes. You shall not breed together two kinds of your cattle; you shall not sow your field with two kinds of seed, nor wear a garment upon you of two kinds of material mixed together."
Shellfish/Lobster - Leviticus 11:10 - "But whatever is in the seas and in the rivers that does not have fins and scales among all the teeming life of the water, and among all the living creatures that are in the water, they are detestable things to you."
Tattoos - Leviticus 19:28 - "You shall not make any cuts in your body for the dead nor make any tattoo marks on yourselves: I am the Lord."
Divorce - Mark 10:9 - "What therefore God has joined together, let no man separate."
None of these things are outlawed in any way. Chances are, you probably eat pigs if you're not vegetarian, and shellfish/lobster if you're not vegan. Even if you are vegan, you've probably worn polyester or other fabric blends before.
The point I'm trying to make here is that the bible is thousands of years old. If homosexuality should be banned because "the bible outlaws it", so should all of the things I listed above.
I too am against divorce.
But the reason why we don't follow those old testament rules(the tradition ones) is explained by Paul in the New Testament(Galatians 3):
"
For as many as are of the works of the law are under the curse: for it is written, Cursed [is] every one that continueth not in all things which are written in the book of the law to do them.
But that no man is justified by the law in the sight of God, [it is] evident: for, The just shall live by faith.
And the law is not of faith: but, The man that doeth them shall live in them."
...
"Wherefore then [serveth] the law? It was added because of transgressions, till the seed should come to whom the promise was made; [and it was] ordained by angels in the hand of a mediator."
"[is] the law then against the promises of God? God forbid: for if there had been a law given which could have given life, verily righteousness should have been by the law.
But the scripture hath concluded all under sin, that the promise by faith of Jesus Christ might be given to them that believe.
But before faith came, we were kept under the law, shut up unto the faith which should afterwards be revealed.
Wherefore the law was our schoolmaster [to bring us] unto Christ, that we might be justified by faith.
But after that faith is come, we are no longer under a schoolmaster.
For ye are all the children of God by faith in Christ Jesus."
This Paul says. It means that it's actually impossible to obey all these traditional commandments. So, we are no longer under the law, but under faith. And faith will cause us to do what God wants.
But just like a teacher, we don't have to do exactly what he said, but we mustn't forget what he said and why.
Many of those rules had to do with traditions out of that time.(The non-jews practiced these things, and God didn't want His people to want to be like them.)
But the reason for Homosexuality is different, and is repeated in the New Testament by Paul himself.
God is speaking trough the Holy Spirit in him that Homosexuality is (one of) the sins that God condemns. No homosexual shall enter Heaven.
This is what the Bible says, and therefore it frustrates me when people who call themselves Christians say things like "I support gays" or even "I am gay".
They make themselves believe that they cannot change, and excuse it with the fact that they're born that way.
Which means they don't confess they're wrong and do the very opposite and find an excuse for it.
One of the things that someone must do who wants to repent, is confess to God he was sinning. So what homosexuals are doing is very far from repentance.