Homosexuality in Leviticus is condemned as ritually impure, an abomination, the same as eating pork. The rules of the Hebrews were designed for a very specific purpose in a very particular setting. They were to stand out as a different people than the others.
In addition: they would honor their parents, keep the Sabbath, forbid cattle interbreeding, forbid sowing fields with two different kinds of seeds, not to wear garments with two different types of materials. Fruit trees could not be harvested on every fifth year and various dietary laws had to be kept. It was a ritual purity, an external one, that would prove the Hebrews as a holy people, different from their neighbors, the Canaanites. Homosexuality in Leviticus is condemned as ritually impure, an abomination, the same as eating pork. An abomination is by definition what the Gentiles do, but that in and of itself is not necessarily evil or a violation of the Commandments.
Thus homosexuality is an abomination in Leviticus not because it is inherently evil but because the Gentiles do it, and it is therefore ritually impure.