I have no idea who this Idan Dershowitz is but his invention published as scholarly wisdom is beyond belief. Dershowitz is attempting to claim that among the many renditions of the text of Leviticus along its way to the version we know today, things changed. What was first allowance for homosexual relations between men because a prohibition later on. And how does he know this, textual evidence, he claims. Textual criticism and those who practice it generally cannot accept the text as we have it and presume to unpack a history that is attested to not in evidence or in fact but in supposition. We must be careful here. We do not have the luxury of being able to press the undo button and see what went before. Even if we did, there is no evidence whatsoever that the undo button would show us anything different than what we have. In fact, every evidence we have sustains and supports the text as we know it to be the ancient text, the authentic text, and the authoritative text. The rest of this is interesting supposition that offers us nothing solid except a guess ventured, a guess so often based less on what is thought to be in the text but upon modern presuppositions and points of view. That is surely the case with Dershowitz. He is guided not by the text but by his desire to see what the text clearly says to be undone.
A better scholar than I has rebuffed Dershowitz and his claims in First Things. You can read Robert Gagnon here.Chapter 18 of Leviticus contains a list of forbidden incestuous acts, followed by prohibitions against sex with a menstruating woman, bestiality and various other sexual acts. In Verse 22, we find its most famous injunction: “You shall not lie with a male as with a woman; it is an abomination.” (Leviticus 20:13 repeats this law, along with a punishment for those who violate it: “They shall be put to death; their blood is upon them.”)Like many ancient texts, Leviticus was created gradually over a long period and includes the words of more than one writer. Many scholars believe that the section in which Leviticus 18 appears was added by a comparatively late editor, perhaps one who worked more than a century after the oldest material in the book was composed. An earlier edition of Leviticus, then, may have been silent on the matter of sex between men.But I think a stronger claim is warranted. As I argue in an article published in the latest issue of the journal Hebrew Bible and Ancient Israel, there is good evidence that an earlier version of the laws in Leviticus 18 permitted sex between men. In addition to having the prohibition against same-sex relations added to it, the earlier text, I believe, was revised in an attempt to obscure any implication that same-sex relations had once been permissible.
My point in all of this is that the typical modern approach is to begin with the assumption that Scripture simply cannot possibly mean what it says and therefore something had to happen to corrupt its intent and its original meaning. Such is the nefarious way of the editor who puts two and two together and comes up with fifteen and one half. And, of course, the moderns insist that the text as we have it could not possibly be from the original authors but has suffered drastic revision by editors and redactors until it is in the shape we have it today -- wholly unreliable and invented. So therefore the Church must turn to the academic to tell us what it really says and what it really means. In this way the exegete cannot possible begin with the textus receptus but must mine its earth for the raw ore of origins. The problem with this raw ore is that it is just as unreliable and unreadable as the text and so we must presume what is not there and read into it what it does not say. In the end we have no word of the Lord at all but our best guesses -- minus miracles, of course. And with such legend, myth, story, opinion, edit and redaction, about the only thing left is morality -- a morality without boundary except what is consensual and what feels right and a morality which insists that what God wants, if there is one, is to thine own self be true. All that work just to get to where culture, society, trend, and fad already are. Seems like too much work to me. Why not dispense with Scripture and simply allow God to speak through desire, want, consent, and feeling? Yup, that is surely the easier path but, alas, it does not have the same authority as "Thus saith the Lord -- we think."