Ever notice that the Christians who cite a literalistic reading of Scripture against homosexuality love to reinterpret or just plain ignore their own holy book on subjects ranging from slavery to polygamy to the status of women? Do they regard the Bible as God's Word, yes or no? If they pick and choose, then their ultimate authority in matters of faith is their standard for picking and choosing, not the Bible itself.
This applies to salad-bar versions of any religion, but Christians seem especially prone to picking and choosing. Fluffy-bunny liberal Christians do it; so do fire-and-brimstone conservative Christians. A good reading of this site might help them.