That’s a very good question. Many of those who insist that the bible or the church or “the Lord” or some other sacred authority condemns in the strongest terms the love and attraction of same-sex partners, often outright dismiss traditions and texts that discourage divorce, that allow polygamy, and that condemn adultery on pain of death. Their prudery is a matter of convenience to justify their prejudices, but they are far from consistent with how they apply ancient rules of sexual behavior.
The shortest but still most accurate answer is probably this: they ignore prohibitions against their lives because they are not willing to live by ancient prescriptions that do not take their interests and circumstances into consideration, but they do weaponize other texts to marginalize those they don’t understand or don’t like in order to maintain an advantage over them in society.
Most conflicts in life usually boil down to money or power, and in this case, it’s power. Religion is used against LGBTQ people to keep them down, as it were, even though the weapons used against them could be used against their accusers who usually don’t apply the texts with as little grace when dealing with their own lives.
