It’s just bigotry, pure and simple.
Religious fundamentalists love to quote Leviticus and use that as their excuse for their anti-gay prejudice. Yet they tend to ignore the other laws and “abominations” found in that same biblical book. As an example:
“For everyone who curses his father or his mother shall surely be put to death. He has cursed his father or his mother. His blood shall be upon him.” (Leviticus 20:9)
“If a man lies with a woman during her sickness and uncovers her nakedness, he has discovered her flow, and she has uncovered the flow of her blood. Both of them shall be cut off from her people.” (Leviticus 20:18)
“Your male and female slaves are to come from the nations around you; from them you may buy slaves. You may also buy some of the temporary residents living among you and members of their clans born in your country, and they will become your property.” (Leviticus 25:44–45)
“Do not cut the hair at the sides of your head or clip off the edges of your beard.” (Leviticus 19:27)
”...and the swine, though it divides the hoof, having cloven hooves, yet does not chew the cud, is unclean to you.” (Leviticus 11:7)
”...do not plant your field with two kinds of seed. Do not wear material woven of two kinds of material.” (Leviticus 19:19)
How many practice all these? Fundamentalists tend to say that these “laws of Moses” were superseded when Christ gave his sermon on the mount. However, they still love to quote this:
“You shall not lie with a male as with a woman. It is an abomination.” (Leviticus 18:22)
Apparently Jesus felt that rule should be untouched. Although it’s funny that Christ never mentions homosexuality in the Bible even once, seeing just how much of an abomination it is.