Recently, I posted a meme on my personal Facebook page that challenged the Christian argument that sex between two men is morally wrong because this is allegedly prohibited in the Old Testament book called Leviticus.
The basic objection in the meme is that there are several things that Leviticus prohibits that Christians seem to have no moral objections against.

• Eating ham or bacon or pork ribs or pork chops or pork roast or pork sausage:

⁷ The pig, for even though it has divided hoofs and is cleft-footed, it does not chew the cud; it is unclean for you. ⁸ Of their flesh you shall not eat, and their carcasses you shall not touch; they are unclean for you. (Leviticus 11:7-8)

• Eating shrimp, crayfish, crab, lobster, clams, scallops, oysters, and mussels:

¹⁰ But anything in the seas or the streams that does not have fins and scales, of the swarming creatures in the waters and among all the other living creatures that are in the waters—they are detestable to you ¹¹ and detestable they shall remain. Of their flesh you shall not eat, and their carcasses you shall regard as detestable. ¹² Everything in the waters that does not have fins and scales is detestable to you. (Leviticus 11:10-12)

• Planting a mixture of two different kinds of seeds or wearing clothes made from two different kinds of material or fabric:

¹⁹ You shall keep my statutes. You shall not let your animals breed with a different kind; you shall not sow your field with two kinds of seed; nor shall you put on a garment made of two different materials.  (Leviticus 19:19)

• Trimming your sideburns or beard:

²⁷ You shall not round off the hair on your temples or mar the edges of your beard. (Leviticus 19:27)

• Getting a tattoo:

²⁸ You shall not make any gashes in your flesh for the dead or tattoo any marks upon you: I am the Lord. (Leviticus 19:28)

• Having sex with a woman when she is on her period:

¹⁹ “‘Do not approach a woman to have sexual relations during the uncleanness of her monthly period. (Leviticus 18:19)

Christians have no interest in passing laws against any of these other things prohibited by Leviticus.  Christians don’t condemn or criticize people who do these other things prohibited by Leviticus.  Christians themselves often openly practice these other things prohibited by Leviticus, and feel no shame in doing so.
One of my Facebook friends is a Catholic, a philosophy student, and an admirer of Aquinas.  He made this comment in response to my posting of the meme:

I asked Christopher how reason alone could show that sex between men was evil, and he responded by pointing me to an article that presented a Thomist argument against homosexual sex.
I plan to analyze and evaluate that argument here on The Secular Outpost later this year, but first I want to deal with the argument against homosexual sex based on quotations from the Old Testament book Leviticus.
Off the top of my head, I came up with a dozen reasons to doubt this argument that is based on the book of Leviticus.  Some of the reasons are indented (namely reasons 3 through 8) because they not only provide some independent reason for doubt, but also provide support for the second reason (i.e. Leviticus is NOT the inspired Word of God.).  So, the list below will provide me with a plan for future posts in this new series of posts.
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A DOZEN REASONS WHY I DOUBT THAT LEVITICUS PROVIDES US WITH A LEGITIMATE MORAL PROHIBITION AGAINST SEX BETWEEN TWO MEN
1. God does NOT exist, so no prophet and no book contains truth or wisdom from God. 
2. Leviticus is NOT the inspired Word of God. (Leviticus is just another book written by ignorant and imperfect human beings).

3. Leviticus was NOT written or authored by Moses.
4. Leviticus is NOT an historically reliable account of actual events.
5. Leviticus contains bad moral guidelines.
6. Leviticus contains bad laws and bad social guidelines.
7. Leviticus contains false information.
8. Leviticus contains logical contradictions.

9. It is unclear and uncertain whether the relevant passages in existing copies of Leviticus are accurate representations of the original text of Leviticus.
10. It is unclear and uncertain whether the relevant passages in existing copies of Leviticus prohibit sex between two men. 
11. Even if the relevant passages in existing copies of Leviticus prohibit sex between two men, it is unclear and uncertain WHY Leviticus prohibits sex between two men.
12. Even if the relevant passages in existing copies of Leviticus prohibit sex between two men, it is unclear and uncertain whether this prohibition applies to Christians, or even to modern Jews.