Robert Gagnon, a professor of New Testament at Pittsburgh Theological Seminary, simply demolishes Lisa Miller's Newsweek article that offered a "biblical" defense of same-sex unions.
Professor Gagnon's demolition is a wonder to behold, a majestic disassembling of a series of horrid arguments. You can find the entire piece here. Here's an excerpt:
A male-female prerequisite is powerfully evident throughout the pages of Scripture. Every biblical narrative, law, proverb, exhortation, metaphor, and poetry that has anything to do with sexual relations presupposes such a prerequisite. Even the male-dominated society of ancient Israel imaged itself as Yahweh’s wife so as to avoid any connotation of a marriage between members of the same sex (an image replicated in the New Testament as regards Christ and his bride, the church). There are plenty of laws in the Old Testament delimiting acceptable and unacceptable sexual relationships between a man and a woman. Never is there any attempt to make such a distinction for same-sex sexual relationships, for the obvious reason that no homosexual relationships are deemed acceptable.
Miller makes much of the fact that the Bible condemns homosexual practice only in “a handful of passages,” while neglecting a number of relevant texts: the narratives of Sodom and of the Levite at Gibeah; the texts from Deuteronomy and the Deuteronomistic History dealing with cultic figures known to play the female role in sex with men (the qedeshim); the interpretation of the Sodom story in Ezekiel, Jude, and 2 Peter; Jesus’ discussion of marriage in Mark 10 (parallel in Matthew 19); and Paul’s mention of “men who lie with a male” in 1 Cor 6:9 and 1 Tim 1:10 (for a discussion of why these texts indict homosexual practice per se go here, pp. 46-50, 56-57, 72-73).
What of Miller’s argument based on frequency of explicit mention? Bestiality is mentioned even less in the Bible than homosexual practice and incest gets only comparable treatment, yet who would be so foolish as to argue that Jews and Christians in antiquity would have regarded sex with an animal or sex with one’s mother as inconsequential offenses? Infrequency of mention is often an indicator that the matter in question is foundational rather than insignificant. You don’t have to talk a lot about something that most everyone agrees with and that few persons, if any, violate.
Scripture’s male-female prerequisite for marriage and its attendant rejection of homosexual behavior is pervasive throughout both Testaments of Scripture (i.e. it is everywhere presumed in sexual discussions even when not explicitly mentioned); it is absolute (i.e. no exceptions are ever given, unlike even incest and polyamory); it is strongly proscribed (i.e. every mention of it in Scripture indicates that it is regarded as a foundational violation of sexual ethics); and it is countercultural (i.e. we know of no other culture in the ancient Near East or Greco-Roman Mediterranean basin more consistently and strongly opposed to homosexual practice). If this doesn’t qualify as a core value in sexual ethics in Scripture, there is no such thing as a core value in any religious or philosophical tradition.