2,000 years ago, the population was low, infant and child mortality rates were high, and death rates were high. The average lifespan was 30. For a man. For a woman, it was even lower due to deaths in childbirth. In order to keep the population up for the species to survive everyone had to have as many babies as possible, therefore, being gay (in the specific part of the world that the Bible takes place in) was taught to be wrong because, very simply, gay people can't reproduce, and in that society that meant that they were virtually useless. The Old Testament was based off of the culture's rules, beliefs, and laws before Jesus came, so yes, it makes sense that the Bible says that being gay is wrong. In those days (and possibly in these days, too) the best way to get people to do what you wanted was to tell them that God wanted them to do (or not do) it.
In the modern world, however, there's no danger at all of the world's population dying out (unless there's some sort of apocalypse - but that has nothing to go with being gay), so the rule stated in the Old Testament is useless.
If you're going to go for the, "The Bible says it so it must be right!" approach, I'm all for it! However, I should probably tell you about a few of the other things the Bible says...
"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)" (Translation: women wearing jeans is sinful)
"Exodus 35:2 For six days, work is to be done, but the seventh day shall be your holy day, a Sabbath of rest to the LORD. Whoever does any work on it must be put to death. " (Translation: If you work on Sunday, you need to die.)
"Deuteronomy 22:20-1 If, however, the charge is true and no proof of the girl’s virginity can be found, she shall be brought to the door of her father’s house and there the men of her town shall stone her to death. She has done a disgraceful thing in Israel by being promiscuous while still in her father’s house." (Translation: If you have sex out of wedlock, your father can and will have you stoned.)
"Do not clip your hair at the temples, nor trim the edges of your beard. (Leviticus 19:27)" (Translation: Don't trim your beard, God doesn't like it.)
"Exodus 21:7
"When a man sells his daughter as a slave, she shall not go free as male slaves do." (Translation: Don’t piss off your dad; he can sell you into slavery forever.)
"Stone disobedient children" (Deuteronomy 21:18-21)" (Uh… I don’t think this needs a translation.)
So, yeah, good luck with that. Any other arguments? I want to add more to my list of gay rights arguments.
