"...many commentators...think that same-sex sexual acts between males were attached to a cult that involved sexual activity and that was practices by the neighboring people (and, implicitly, by the Israelites themselves!). The surprising reference to child sacrifice in a list of sexual offences strengthens the impression that there is a cultic background. It has been commonly assumed, therefore, that the writers of the Holiness Code associated homoerotic behavior with sex connected to cultic practices." (39)
Under this interpretation, what is at issue is the worship of other gods and the activities related to that worship.
1. The prohibition of sexual contact between males in the Holiness Code in Leviticus 18:22 and 20:13 is done in a context of a polemic against a non-Israelite cult. Because the records of cultic homoeroticism are scanty and not unequivocal, however, historical description of this context is difficult.2. The strategy of postexilic Israelites to maintain their distinct identity by, among other ways, separating from others strengthened the already existing taboos and social standards regarding sexual behavior and gender roles, banning, for instance, castration, cross-dressing, and male same-sex behavior; it was not simply the 'objective' facts of physiology that established gender identity.3. Israel shared with its cultural environment an understanding of sexual life as an interaction between active masculine and passive feminine gender roles. This interaction was the cornerstone of gender identity, but the concept of sexual orientation was unkown. Sexual contact between two men was prohibited because the passive party assumed the role of a woman and his manly honor was thus disgraced.
From Martti Nissinen's Homoeroticism in the Biblical World: A Historical Perspective, 44.
Nissinen's book is lovely and I'd recommend it to anyone who wants to start thinking about sexuality in the ancient near east. The presence of these two verses in Hebrew scripture have created all sorts of arguments, proof-texts, etc. but rarely with an appreciation for the context, which is admittedly difficult to pin down. Of course, if you want to go with "The Bible says..." as an argument without an appreciation for what it might mean within its context, then those within the Christian faith who do not see homosexual activity as potentially viable and faithful would have to limit themselves to opposing male same-sex acts. I won't hold my breath for conservative Christians to welcome lesbianism.