In this article Markels displays a certain confusion about the word toevah, translated "abomination" in those passages.
God gave the Jewish people 613 mitzvot in the Torah ... and within them, there are the directives that are called in Hebrew "toevah".... Translated to mean everything from an "abomination" to something "ritually unclean," this "Holiness Code" identifies more than 120 of these instructions for behavior. ... Toevah includes the rules of kashrut, or kosher dietary regulations, which prohibit eating shellfish or pork or mixing meat and milk.
Well, with this amount of error, it's hard to know where to start. The most important correction to make against Markels is that toevah does not at all refer to ritual uncleanness. Even a cursory reading of the Torah in Hebrew will reveal that the vocabulary of the ritual approach to God is based on the poles of "purity, cleanness" (denoted by the word tohorah, טהרה) and "uncleanness, impurity" (tumah, טמאה). Toevah is just not part of this system. Ritual uncleanness can be got rid of by various means -- washings, sacrifices, etc. Whatever is toevah can only be shunned.
In Leviticus, toevah is not used for 120 rules of behavior; in fact, the word only appears 6 times in the book, and specifically of an act only in Lev. 18:22 and 20:13 quoted above. In Deuteronomy, on the other hand, it appears 17 times and is used more loosely. It is all too common, in and out of scholarship (such as here and here), to take the Deuteronomic usage (which does indeed use the word for non-kosher foods, Deut. 14:3) and apply it to Leviticus, as if the two texts were homogeneous.
Deuteronomy, it should be remembered, is a sermonic exhortation to keep all of God's law, a perspective that allowed the author to view even ceremonial infractions as displaying an attitude potentially dishonoring to God and therefore calling for moral censure. Leviticus, on the other hand, is not written in the sermonic mode and is obligated to use more exact language.
A survey of all the 116 usages of toevah in the Hebrew Bible shows, I think, that the term is overwhelmingly used as a term of moral opprobrium. I think that includes Leviticus. I won't go into all the texts. This is a philological issue that has unfortunately gotten tangled with the politics of equal rights. The temptation to defuse an explosive text by any means possible because it does not mesh with certain social or political aspirations (however laudable) is difficult to resist. But the effort should be made.