Here's why (from another post):
Next time some idiot brings this passage up - tell them that you proudly engage in as much homosexual sex as humanly possible, and here's why:
Leviticus 18:22 states: "Thou shall not lie with mankind as with womankind: it is abomination." The term abomination (to'ebah) is a religious term, usually reserved for use against idolatry; it does not mean a moral evil. The verse seems to refer to temple prostitution, which was a common practice in the rest of the Middle East at that time. Qadesh referred to male religious prostitutes. (See the discussion of Deuteronomy)
Leviticus 20:13 states: "If a man also lie with mankind as he lieth with a woman, both of them have committed an abomination; they should surely be put to death....". The passage is surrounded by prohibitions against incest, bestiality, adultery and intercourse during a woman's period. But this verse is the only one in the series which uses the religious term abomination; it seems also to be directed against temple prostitution.
These passages are part of the Jewish Holiness Code which also:
permits polygamy
prohibits sexual intercourse when a woman has her period,
bans tattoos
prohibits eating rare meat
bans wearing clothes that are made from a blend of textiles
prohibits cross-breeding livestock
bans sowing a field with mixed seed
prohibits eating pigs, rabbits, or some forms of seafood
requires Saturday to be reserved as the Sabbath
Churches have abandoned the Holiness Code; it is no longer binding on modern-day Christians. They can wear tattoos, eat shrimp, wear polyester-cotton blends and engage in temple prostitution without violating this particular section of the Bible. Although this code is obsolete for Christians, many clergy still focus on those passages which deal with homosexuality.<1>
I got this from Whosoever.org
http://www.whosoever.org/bible/lev18.html