It should be mandatory for Christians to read the Bible in its entirety. Too often, it is cherry-picked in a way that makes it apparent that many have not read it in chronological order.
I don't mean that reading it in chronological order will somehow impart a perfect understanding. The Christian Bible is not perfect. Most Christians are reading it in translation and in societies radically different from those of the ancient Hebrews and early Christians, losing much of the wordplay and intent of the original Hebrew, Aramaic, and Greek. It is entirely possible parts of it are made up, as well, such as the name Bartemaeus. Much of it was oral for long periods, and everyone knows how most games of Telephone end. But if there is one thing that can be learned from reading the Bible in its entirety it is that Christians are not banned from practicing homosexuality, especially not female homosexuality.
When I was a kid, I decided I was going to read the entire Bible because I liked reading and being a smartass, and what better way to be a smartass than to correct your Sunday school teacher? So I started reading from Genesis and quickly fell in love with the insanity of the Pentateuch, the first five books of the Bible.
Now, there's this little book called Leviticus which contains both the Ten Commandments and a whole bunch of other laws that, weirdly, most Christians don't think they have to follow. Moses was pretty clear in Deuteronomy that those who did not follow the laws would be cursed (the Bible is hardcore, fyi). There is one, however, that many Christians think is forbidden: homosexuality. This magical, super special law is supposedly supported by the incident in Genesis of Sodom and Gomorrah, a story that ends in neutrally-portrayed, daughter-on-father rape. This is notable here because father-daughter incest is forbidden under the mitzvot, making it very hard to use this part of the Bible as a benchmark for good and bad.
The reason I took so long to figure out why Christians thought they were special enough to ignore all the mitzvot was because, well, Matthew, Mark, Luke, and John bored me to tears, and I thought the word epistle sounded pompous and douchey. So I skipped around, read Revelations, and didn't look back.
Unfortunately for me, the Epistles are the straightforward part of the New Testament, the part where the theology is really laid out. The Gospels are basically a collection of biographies, the Acts of the Apostles being spinoffs where the side characters get some air time, and Revelations is the bad acid trip of some dude named John.
Anyway, near the beginning of the Epistles, about halfway through the New Testament, is the Epistle to the Galatians, an angry letter Paul of Tarsus (the donkey dude) wrote to set a bunch of Galatians (possibly Gauls but no one's sure). In it, he said, "Christ redeemed us from the curse of the law by becoming a curse for us" and "the law was our guardian until Christ came that we might be justified by faith. Now that this faith has come, we are no longer under a guardian." That is to say, Jesus sacrificing himself does away with the mitzvot including the Ten Commandments, although Jesus reiterated some of the Ten Commandments in Matthew 19:18-19, making it a possible interpretation that they were all to be followed.
So what does this have to do with homosexuality?
For one, female homosexuality is not explicitly mentioned in the Bible. There are several extremely ambiguous lines in Romans 1, "Because of this, God gave them over to shameful lusts. Even their women exchanged natural sexual relations for unnatural ones. In the same way the men also abandoned natural relations with women and were inflamed with lust for one another", but the fact that "even their women" precedes the bit about male homosexuality.... Like I said, ambiguous. Since this chapter is understood to be about Sodom and Gomorrah, which has a serious case of conflicting morals, and is a retelling written hundreds, maybe thousands, of years after the fact, we can throw it out and just say the Bible doesn't mention girl-on-girl action.
Male homosexuality, obviously, is addressed. There's Sodom and Gomorrah and the New Testament retelling, which are, once again, problematic enough to be ignored. The mitzvot are explicit in telling dudes that they can't have sex with men in general, and everyone's banned from getting it on with their dad and their dad's brother. As Paul so helpfully informed the Galatians, though, Christians aren't required to follow anything written in Leviticus or Deuteronomy.
And I think I just proved that Christians have a green light on incest. Shit.
Um. Anywho, Christians are no more banned from male homosexuality under the Bible than they are from eating bacon-wrapped shrimp with their cheese-coated, tattooed hands as they drive to work on a Sunday. Just so long as they love God and their neighbors.